Re: Rietveld ESD calc fortran code typo?

[Matthew Rowles]

Thanks a lot for that Jonathon.

The code is helping me understand the algorithm, in particular the
implementation of the double sum.

Currently in the process of reproducing it in python to get around my
essentially complete lack of knowledge in fortran so I can properly
understand it.

On Thu, 16 May 2024 at 22:44, Jonathan WRIGHT  wrote:

> Dear Matthew
>
> That fortran snippet was corrected in Appendix 1 of Andreev's paper here:
>
> https://doi.org/10.1107/S002188989300891X
>
> It is a shame that implicit none was not part of fortran 77. The google
> search
> resul leading me to that was:
>
>
> https://www.researchgate.net/publication/359342753_Program_RietESD_for_correction_of_estimated_standard_deviations_obtained_in_Rietveld-refinement_programs
>
> https://www.iucr.org/resources/other-directories/software/rietesd
>
> Presumably similar things are computed as SCOR in fullprof output list
> files
> (Serial CORelation). There is some discussion in Hill and Madsen:
>
> https://doi.org/10.1107/S0021889886090076
>
> ... who give the citations for Pawley 1980 and Scott 1983 to locate the
> origins
> of those estimates.
>
> Best regards,
>
> Jon
>
>
>
> On 14/05/2024 10:56, Matthew Rowles wrote:
> > Hi all
> >
> > Just been reading Berar & Lelann (J Appl Cryst 24:1-5).
> >
> > In the paper's appendix, there is some Fortran code implementing their
> ESD
> > multiplier calculation.
> > This code was added to the end of the CHISQ subroutine in DBW3.2
> >
> > I'm interested in line 10:
> > COREL = (DEL**2/Y(I)) + CD
> >
> > Should CD be XD? Is this a typo?
> >
> > If not, does anyone know what CD represents?
> >
> > image.png
> >
> >
> > Thanks
> >
> >
> > Matthew
> >
> >
> > ++
> > Please do NOT attach files to the whole list
> 
> > Send commands to  eg: HELP as the subject with no body
> text
> > The Rietveld_L list archive is on
> http://www.mail-archive.com/rietveld_l@ill.fr/
> > ++
> >
> ++
> Please do NOT attach files to the whole list  >
> Send commands to  eg: HELP as the subject with no body
> text
> The Rietveld_L list archive is on
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++
>
>
++
Please do NOT attach files to the whole list 
Send commands to  eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++

Re: Rietveld ESD calc fortran code typo?

[Jonathan WRIGHT]

Dear Matthew

That fortran snippet was corrected in Appendix 1 of Andreev's paper here:

https://doi.org/10.1107/S002188989300891X

It is a shame that implicit none was not part of fortran 77. The google search 
resul leading me to that was:


https://www.researchgate.net/publication/359342753_Program_RietESD_for_correction_of_estimated_standard_deviations_obtained_in_Rietveld-refinement_programs

https://www.iucr.org/resources/other-directories/software/rietesd

Presumably similar things are computed as SCOR in fullprof output list files 
(Serial CORelation). There is some discussion in Hill and Madsen:


https://doi.org/10.1107/S0021889886090076

... who give the citations for Pawley 1980 and Scott 1983 to locate the origins 
of those estimates.


Best regards,

Jon



On 14/05/2024 10:56, Matthew Rowles wrote:

Hi all

Just been reading Berar & Lelann (J Appl Cryst 24:1-5).

In the paper's appendix, there is some Fortran code implementing their ESD 
multiplier calculation.

This code was added to the end of the CHISQ subroutine in DBW3.2

I'm interested in line 10:
    COREL = (DEL**2/Y(I)) + CD

Should CD be XD? Is this a typo?

If not, does anyone know what CD represents?

image.png


Thanks


Matthew


++
Please do NOT attach files to the whole list 
Send commands to  eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++

++
Please do NOT attach files to the whole list 
Send commands to  eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++

Re: Rietveld condamnation considered as established by some more people

[Le Bail Armel]

Indeed, saying "back to that" with some disdain reveals your are the physicist interested by properties of already structurally known compounds.The crystallographer says "towards the posibility to solve the structure of unknowncompounds" and for that you need the structure factors. Then comes the Rietveld refinement anyway.envoyé : 18 août 2023 à 17:00de : Alan W Hewat à : Le Bail Armel cc : "rietveld_l@ill.fr" objet : Re: Rietveld condamnation considered as established by some more peopleI have no problem with Rietveld's prize Armel. Crystallographers ignored the method for too long, fixated as they were on "structure factors". Even your own method harks back to that. The idea that physical parameters could be refined directly from the data is more a physicist's idea, which makes me think that physicists Loopstra and Van Laar had essential input. Rietveld was a crystallographer. In retrospect the prize might have been awarded to the trio, but in retrospect we also simplify reality.Dr Alan Hewat, NeutronOpticsGrenoble, FRANCE (from phone)alan.he...@neutronoptics.com+33.476984168 VAT:FR79499450856http://NeutronOptics.com/hewat___   On Fri, 18 Aug 2023, 15:15 Le Bail Armel, <le-bail.ar...@orange.fr> wrote:I would be curious if the Royal Swedish Academy of Sciences has archivesconcerning this Gregori Aminoff 1995 Prize decision/investigation :http://www.cristal.org/rietv025/foto3.jpgWho was contacted as reference ? Was Loopstra contacted and if yes, anypositive answer from him ?;-)envoyé : 18 août 2023 à 11:30de : Alan W Hewat <alan.he...@neutronoptics.com>à : Le Bail Armel <le-bail.ar...@orange.fr>cc : rietveld_l@ill.frobjet : Re: Rietveld condamnation considered as established by some more peopleBonjour Armel.No, it was van Laar who initiated it. He was annoyed that I had praised Rietveld too much in my own accounts. http://hewat.net/science/ill-hewat.html 'History of the ILL from a personal perspective'.https://journals.iucr.org/j/issues/2016/04/00/es0421/ 'Hugo Rietveld (1932–2016)'  Alan Hewat, William I. F. David and Lambert van Eijck He sent me a draft paper that he proposed to publish, but I suggested a less critical version. He agreed, and later involved Henk Schenk in producing a softer version. So it's the opposite to what you assume - Van Laar's original paper was toned down in the joint paper:https://scripts.iucr.org/cgi-bin/paper?ib5058 "The development of powder profile refinement at the Reactor Centre Netherlands at Petten" Bob van Laar and Henk SchenkWhy don't you write to van Laar and ask for a copy of his original version (abstract below)Facts about the Profile refinement method in Powder diffraction.Bob van Laar, AmsterdamJustification of the present paperThe aim of this paper is to give detailed historical insight in the procedure that led to thedevelopment of the profile refinement of neutron powder data, since then known as the'Rietveld method'. The present paper has been written by the last person still alive, involvedin the development of this method (Loopstra died in november 1998). The purpose is tocorrect some incorrectness's that have been connected to the method in course of time.Kind regards, Alan.On Fri, 18 Aug 2023 at 10:51, Le Bail Armel <le-bail.ar...@orange.fr> wrote:Bonjour Alan,My problem with the Bob van Laar and Henk Schenk paper is that it would have beencredible if signed by van Laar alone or better by Loopstra and van Laar and also ifpublished before 1980 or 1990, not in 2018.That 2018 paper looks strongly as initiated by Henk Schenk and the main argumentsinside are from old Rietveld-Schenk interferences, especially the story when Rietveld refused to plaid guilty after being accused by Schenk in a very strange manner.Now, the fact that Schenk was IUCr President may be sufficient for many people tobelieve in his version of the story. It was not sufficient for Hugo Rietveld and it is notsufficient for me.BestArmelPS - Why to insert a reference to the 1981 Pawley paper in a 1988 paper where hismethod was not used but another method much later named "Le Bail method" andbased on the Rietveld (Loopstra ??? proove it please) decomposition formula ?envoyé : 16 août 2023 à 19:08de : Alan W Hewat <alan.he...@neutronoptics.com>à : Le Bail Armel <le-bail.ar...@orange.fr>cc : "rietveld_l@ill.fr" <rietveld_l@ill.fr>objet : Re: Rietveld condamnation considered as established by some more peopleBonjour Armel. In answer to your question "Where did they find the text of the judgement ?" please see:"The development of powder profile refinement at the Reactor Centre Netherlands at Petten" Bob van Laar and Henk Schenkhttps://scripts.iucr.org/cgi-bin/paper?ib5058Van Laar worked at Petten with Rietveld, and Schenk was the IUCr president. This paper is apparently the basis of Mittemeijer's

Re: Rietveld condamnation considered as established by some more people

[Alan W Hewat]

I have no problem with Rietveld's prize Armel. Crystallographers ignored
the method for too long, fixated as they were on "structure factors". Even
your own method harks back to that. The idea that physical parameters could
be refined directly from the data is more a physicist's idea, which makes
me think that physicists Loopstra and Van Laar had essential input.
Rietveld was a crystallographer. In retrospect the prize might have been
awarded to the trio, but in retrospect we also simplify reality.


Dr Alan Hewat, NeutronOptics
Grenoble, FRANCE (from phone)
alan.he...@neutronoptics.com
+33.476984168 VAT:FR79499450856
http://NeutronOptics.com/hewat
___


On Fri, 18 Aug 2023, 15:15 Le Bail Armel,  wrote:

> I would be curious if the Royal Swedish Academy of Sciences has archives
>
> concerning this Gregori Aminoff 1995 Prize decision/investigation :
>
> http://www.cristal.org/rietv025/foto3.jpg
>
> Who was contacted as reference ? Was Loopstra contacted and if yes, any
>
> positive answer from him ?
>
> ;-)
>
>
>
> *envoyé :* 18 août 2023 à 11:30
> *de :* Alan W Hewat 
> *à :* Le Bail Armel 
> *cc :* rietveld_l@ill.fr
> *objet :* Re: Rietveld condamnation considered as established by some
> more people
>
> Bonjour Armel.
>
> No, it was van Laar who initiated it. He was annoyed that I had praised
> Rietveld too much in my own accounts.
> http://hewat.net/science/ill-hewat.html* 'History of the ILL from a
> personal perspective'.*
> https://journals.iucr.org/j/issues/2016/04/00/es0421/ '*Hugo Rietveld
> (1932–2016)'*  Alan Hewat, William I. F. David and Lambert van Eijck
>  He sent me a draft paper that he proposed to publish, but I suggested
> a less critical version. He agreed, and later involved Henk Schenk in
> producing a softer version. So it's the opposite to what you assume - Van
> Laar's original paper was toned down in the joint paper:
> https://scripts.iucr.org/cgi-bin/paper?ib5058 "*The development of powder
> profile refinement at the Reactor Centre Netherlands at Petten*"
> Bob van Laar and Henk Schenk
>
> *Why don't you write to van Laar and ask for a copy of his original
> version (abstract below)*
>
>
>
> *Facts about the Profile refinement method in Powder diffraction.Bob van
> Laar, Amsterdam*Justification of the present paper
>
>
>
>
> *The aim of this paper is to give detailed historical insight in the
> procedure that led to thedevelopment of the profile refinement of neutron
> powder data, since then known as the'Rietveld method'. The present paper
> has been written by the last person still alive, involvedin the development
> of this method (Loopstra died in november 1998). The purpose is tocorrect
> some incorrectness's that have been connected to the method in course of
> time.*
>
> Kind regards, Alan.
>
> On Fri, 18 Aug 2023 at 10:51, Le Bail Armel 
> wrote:
>
> Bonjour Alan,
>
> My problem with the Bob van Laar and Henk Schenk paper is that it would
> have been
>
> credible if signed by van Laar alone or better by Loopstra and van Laar
> and also if
>
> published before 1980 or 1990, not in 2018.
>
> That 2018 paper looks strongly as initiated by Henk Schenk and the main
> arguments
>
> inside are from old Rietveld-Schenk interferences, especially the story
> when Rietveld
>
> refused to plaid guilty after being accused by Schenk in a very strange
> manner.
>
> Now, the fact that Schenk was IUCr President may be sufficient for many
> people to
>
> believe in his version of the story. It was not sufficient for Hugo
> Rietveld and it is not
>
> sufficient for me.
>
> Best
>
> Armel
>
> PS - Why to insert a reference to the 1981 Pawley paper in a 1988 paper
> where his
>
> method was not used but another method much later named "Le Bail method"
> and
>
> based on the Rietveld (Loopstra ??? proove it please) decomposition
> formula ?
>
> *envoyé :* 16 août 2023 à 19:08
> *de :* Alan W Hewat 
> *à :* Le Bail Armel 
> *cc :* "rietveld_l@ill.fr" 
> *objet :* Re: Rietveld condamnation considered as established by some
> more people
>
> Bonjour Armel.
>
> In answer to your question "Where did they find the text of the judgement
> ?" please see:
> "The development of powder profile refinement at the Reactor Centre
> Netherlands at Petten"
> Bob van Laar and Henk Schenk
> https://scripts.iucr.org/cgi-bin/paper?ib5058
>
> Van Laar worked at Petten with Rietveld, and Schenk was the IUCr
> president. This paper is apparently the basis of Mittemeijer's book. His
> point is that scientific discoveries are often the result of

Re: Rietveld condamnation considered as established by some more people

[Le Bail Armel]

I would be curious if the Royal Swedish Academy of Sciences has archivesconcerning this Gregori Aminoff 1995 Prize decision/investigation :http://www.cristal.org/rietv025/foto3.jpgWho was contacted as reference ? Was Loopstra contacted and if yes, any positive answer from him ?;-)envoyé : 18 août 2023 à 11:30de : Alan W Hewat à : Le Bail Armel cc : rietveld_l@ill.frobjet : Re: Rietveld condamnation considered as established by some more peopleBonjour Armel.No, it was van Laar who initiated it. He was annoyed that I had praised Rietveld too much in my own accounts. http://hewat.net/science/ill-hewat.html 'History of the ILL from a personal perspective'.https://journals.iucr.org/j/issues/2016/04/00/es0421/ 'Hugo Rietveld (1932–2016)'  Alan Hewat, William I. F. David and Lambert van Eijck He sent me a draft paper that he proposed to publish, but I suggested a less critical version. He agreed, and later involved Henk Schenk in producing a softer version. So it's the opposite to what you assume - Van Laar's original paper was toned down in the joint paper:https://scripts.iucr.org/cgi-bin/paper?ib5058 "The development of powder profile refinement at the Reactor Centre Netherlands at Petten" Bob van Laar and Henk SchenkWhy don't you write to van Laar and ask for a copy of his original version (abstract below)Facts about the Profile refinement method in Powder diffraction.Bob van Laar, AmsterdamJustification of the present paperThe aim of this paper is to give detailed historical insight in the procedure that led to thedevelopment of the profile refinement of neutron powder data, since then known as the'Rietveld method'. The present paper has been written by the last person still alive, involvedin the development of this method (Loopstra died in november 1998). The purpose is tocorrect some incorrectness's that have been connected to the method in course of time.Kind regards, Alan.On Fri, 18 Aug 2023 at 10:51, Le Bail Armel <le-bail.ar...@orange.fr> wrote:Bonjour Alan,My problem with the Bob van Laar and Henk Schenk paper is that it would have beencredible if signed by van Laar alone or better by Loopstra and van Laar and also ifpublished before 1980 or 1990, not in 2018.That 2018 paper looks strongly as initiated by Henk Schenk and the main argumentsinside are from old Rietveld-Schenk interferences, especially the story when Rietveld refused to plaid guilty after being accused by Schenk in a very strange manner.Now, the fact that Schenk was IUCr President may be sufficient for many people tobelieve in his version of the story. It was not sufficient for Hugo Rietveld and it is notsufficient for me.BestArmelPS - Why to insert a reference to the 1981 Pawley paper in a 1988 paper where hismethod was not used but another method much later named "Le Bail method" andbased on the Rietveld (Loopstra ??? proove it please) decomposition formula ?envoyé : 16 août 2023 à 19:08de : Alan W Hewat <alan.he...@neutronoptics.com>à : Le Bail Armel <le-bail.ar...@orange.fr>cc : "rietveld_l@ill.fr" <rietveld_l@ill.fr>objet : Re: Rietveld condamnation considered as established by some more peopleBonjour Armel. In answer to your question "Where did they find the text of the judgement ?" please see:"The development of powder profile refinement at the Reactor Centre Netherlands at Petten" Bob van Laar and Henk Schenkhttps://scripts.iucr.org/cgi-bin/paper?ib5058Van Laar worked at Petten with Rietveld, and Schenk was the IUCr president. This paper is apparently the basis of Mittemeijer's book. His point is that scientific discoveries are often the result of the work of many people, yet we tend to simplify the process and attribute them to individual heros. Mike Glazer is simply reviewing his book.Salutations, Alan Dr Alan Hewat, NeutronOpticsGrenoble, FRANCE (from phone)alan.he...@neutronoptics.com+33.476984168 VAT:FR79499450856http://NeutronOptics.com/hewat___   On Wed, 16 Aug 2023, 18:45 Le Bail Armel, <le-bail.ar...@orange.fr> wrote:In a book :How Science Runs – Impressions from a Scientific Career. By Eric J. MittemeijerReviewed by Mike Glazer"In another section, the author has some criticism about the famous Rietveld method in powder diffraction. He points out that the original idea for this method was put forward by Bert O. Loopstra, who later discussed the idea of whole-pattern fitting with Bob van Laar. In order to create a computer program to carry out the method, they hired the computer-savvy Hugo M. Rietveld. The first paper by Loopstra and Rietveld was published in Acta Crystallographica in 1969, having been submitted in 1968. A later paper published in 1969 by Rietveld alone in Journal of Applied Crystallography is the one that is always quoted and led to the name ‘Rietveld method’ or ‘Rietveld refinement’. Mittemeijer points out that this did grave injustice to the origi

Re: Rietveld condamnation considered as established by some more people

[Lambert van Eijck]

dear all,

it is likely that Van Laar was triggered by a visit from me and Bram Schierbeek 
(Dutch Crystallographic Society) around 2016. As Bill David pointed out in 
2015, the year 2016 was approximately 100 years after the 'invention of powder 
diffraction' and approximately 50 years after 'the invention of Rietveld 
refinement'. Unaware of the history of the development of the method at Petten 
(NL), Bram and me visited both Hugo Rietveld and Bob van Laar in 2015/2016, 
with the intention to organize a celebration symposium "Debye & Rietveld: 
100&50 years" in Amsterdam. We soon learned that the different opinions on the 
roles in realizing the method were not reconcilable.  In my personal opinion, 
this celebration event was not the stage to start criticizing the role of Hugo 
Rietveld in the development of the method. The publication by Van Laar and 
Schenk might therefore also have been triggered by our (naive) visit and/or by 
the celebration that took place in Amsterdam.

with best regards,

Lambert van Eijck

Delft


On 18-08-2023 11:30, Alan W Hewat wrote:
Bonjour Armel.

No, it was van Laar who initiated it. He was annoyed that I had praised 
Rietveld too much in my own accounts.
http://hewat.net/science/ill-hewat.html<https://urldefense.com/v3/__http://hewat.net/science/ill-hewat.html__;!!PAKc-5URQlI!7lzeLdY-y1qCjmyDiCGyPrpvkAjE1SBHQB3CYCwzzMMJEAmBxRZJWqFCIgPcDOs0pFt-cAjxMfRIYEkCZnXiFWI_IcBXLQ$>
 'History of the ILL from a personal perspective'.
https://journals.iucr.org/j/issues/2016/04/00/es0421/<https://urldefense.com/v3/__https://journals.iucr.org/j/issues/2016/04/00/es0421/__;!!PAKc-5URQlI!7lzeLdY-y1qCjmyDiCGyPrpvkAjE1SBHQB3CYCwzzMMJEAmBxRZJWqFCIgPcDOs0pFt-cAjxMfRIYEkCZnXiFWKAXaNvpA$>
 'Hugo Rietveld (1932–2016)'  Alan Hewat, William I. F. David and Lambert van 
Eijck
 He sent me a draft paper that he proposed to publish, but I suggested a less 
critical version. He agreed, and later involved Henk Schenk in producing a 
softer version. So it's the opposite to what you assume - Van Laar's original 
paper was toned down in the joint paper:
https://scripts.iucr.org/cgi-bin/paper?ib5058<https://urldefense.com/v3/__https://scripts.iucr.org/cgi-bin/paper?ib5058__;!!PAKc-5URQlI!7lzeLdY-y1qCjmyDiCGyPrpvkAjE1SBHQB3CYCwzzMMJEAmBxRZJWqFCIgPcDOs0pFt-cAjxMfRIYEkCZnXiFWJSotPttA$>
 "The development of powder profile refinement at the Reactor Centre 
Netherlands at Petten"
Bob van Laar and Henk Schenk

Why don't you write to van Laar and ask for a copy of his original version 
(abstract below)

Facts about the Profile refinement method in Powder diffraction.
Bob van Laar, Amsterdam
Justification of the present paper
The aim of this paper is to give detailed historical insight in the procedure 
that led to the
development of the profile refinement of neutron powder data, since then known 
as the
'Rietveld method'. The present paper has been written by the last person still 
alive, involved
in the development of this method (Loopstra died in november 1998). The purpose 
is to
correct some incorrectness's that have been connected to the method in course 
of time.

Kind regards, Alan.

On Fri, 18 Aug 2023 at 10:51, Le Bail Armel 
mailto:le-bail.ar...@orange.fr>> wrote:

Bonjour Alan,

My problem with the Bob van Laar and Henk Schenk paper is that it would have 
been

credible if signed by van Laar alone or better by Loopstra and van Laar and 
also if

published before 1980 or 1990, not in 2018.

That 2018 paper looks strongly as initiated by Henk Schenk and the main 
arguments

inside are from old Rietveld-Schenk interferences, especially the story when 
Rietveld

refused to plaid guilty after being accused by Schenk in a very strange manner.

Now, the fact that Schenk was IUCr President may be sufficient for many people 
to

believe in his version of the story. It was not sufficient for Hugo Rietveld 
and it is not

sufficient for me.

Best

Armel

PS - Why to insert a reference to the 1981 Pawley paper in a 1988 paper where 
his

method was not used but another method much later named "Le Bail method" and

based on the Rietveld (Loopstra ??? proove it please) decomposition formula ?

envoyé : 16 août 2023 à 19:08
de : Alan W Hewat 
mailto:alan.he...@neutronoptics.com>>
à : Le Bail Armel mailto:le-bail.ar...@orange.fr>>
cc : "rietveld_l@ill.fr<mailto:rietveld_l@ill.fr>" 
mailto:rietveld_l@ill.fr>>
objet : Re: Rietveld condamnation considered as established by some more people

Bonjour Armel.

In answer to your question "Where did they find the text of the judgement ?" 
please see:
"The development of powder profile refinement at the Reactor Centre Netherlands 
at Petten"
Bob van Laar and Henk Schenk
https://scripts.iucr.org/cgi-bin/paper?ib5058<https://urldefense.com/v3/__https://scripts.iucr.org/cgi-bin/paper?ib5058__;!!PAKc-5URQlI!7lzeLdY-y1qCjmyDiCGyPrpvkAjE1SBHQB3CYCwzzMMJEAmBxRZJW

Re: Rietveld condamnation considered as established by some more people

[Alan W Hewat]

Bonjour Armel.

No, it was van Laar who initiated it. He was annoyed that I had praised
Rietveld too much in my own accounts.
http://hewat.net/science/ill-hewat.html* 'History of the ILL from a
personal perspective'.*
https://journals.iucr.org/j/issues/2016/04/00/es0421/ '*Hugo Rietveld
(1932–2016)'*  Alan Hewat, William I. F. David and Lambert van Eijck
 He sent me a draft paper that he proposed to publish, but I suggested
a less critical version. He agreed, and later involved Henk Schenk in
producing a softer version. So it's the opposite to what you assume - Van
Laar's original paper was toned down in the joint paper:
https://scripts.iucr.org/cgi-bin/paper?ib5058 "*The development of powder
profile refinement at the Reactor Centre Netherlands at Petten*"
Bob van Laar and Henk Schenk

*Why don't you write to van Laar and ask for a copy of his original version
(abstract below)*



*Facts about the Profile refinement method in Powder diffraction.Bob van
Laar, Amsterdam*Justification of the present paper




*The aim of this paper is to give detailed historical insight in the
procedure that led to thedevelopment of the profile refinement of neutron
powder data, since then known as the'Rietveld method'. The present paper
has been written by the last person still alive, involvedin the development
of this method (Loopstra died in november 1998). The purpose is tocorrect
some incorrectness's that have been connected to the method in course of
time.*

Kind regards, Alan.

On Fri, 18 Aug 2023 at 10:51, Le Bail Armel  wrote:

> Bonjour Alan,
>
> My problem with the Bob van Laar and Henk Schenk paper is that it would
> have been
>
> credible if signed by van Laar alone or better by Loopstra and van Laar
> and also if
>
> published before 1980 or 1990, not in 2018.
>
> That 2018 paper looks strongly as initiated by Henk Schenk and the main
> arguments
>
> inside are from old Rietveld-Schenk interferences, especially the story
> when Rietveld
>
> refused to plaid guilty after being accused by Schenk in a very strange
> manner.
>
> Now, the fact that Schenk was IUCr President may be sufficient for many
> people to
>
> believe in his version of the story. It was not sufficient for Hugo
> Rietveld and it is not
>
> sufficient for me.
>
> Best
>
> Armel
>
> PS - Why to insert a reference to the 1981 Pawley paper in a 1988 paper
> where his
>
> method was not used but another method much later named "Le Bail method"
> and
>
> based on the Rietveld (Loopstra ??? proove it please) decomposition
> formula ?
>
> *envoyé :* 16 août 2023 à 19:08
> *de :* Alan W Hewat 
> *à :* Le Bail Armel 
> *cc :* "rietveld_l@ill.fr" 
> *objet :* Re: Rietveld condamnation considered as established by some
> more people
>
> Bonjour Armel.
>
> In answer to your question "Where did they find the text of the judgement
> ?" please see:
> "The development of powder profile refinement at the Reactor Centre
> Netherlands at Petten"
> Bob van Laar and Henk Schenk
> https://scripts.iucr.org/cgi-bin/paper?ib5058
>
> Van Laar worked at Petten with Rietveld, and Schenk was the IUCr
> president. This paper is apparently the basis of Mittemeijer's book. His
> point is that scientific discoveries are often the result of the work of
> many people, yet we tend to simplify the process and attribute them to
> individual heros. Mike Glazer is simply reviewing his book.
>
> Salutations, Alan
> 
> Dr Alan Hewat, NeutronOptics
> Grenoble, FRANCE (from phone)
> alan.he...@neutronoptics.com
> +33.476984168 VAT:FR79499450856
> http://NeutronOptics.com/hewat
> ___
>
>
> On Wed, 16 Aug 2023, 18:45 Le Bail Armel,  wrote:
>
> In a book :
> How Science Runs – Impressions from a Scientific Career. By Eric J.
> Mittemeijer
>
>
> Reviewed by Mike Glazer
>
>
> "In another section, the author has some criticism about the famous
> Rietveld method in powder diffraction. He points out that the original idea
> for this method was put forward by Bert O. Loopstra, who later discussed
> the idea of whole-pattern fitting with Bob van Laar. In order to create a
> computer program to carry out the method, they hired the computer-savvy
> Hugo M. Rietveld. The first paper by Loopstra and Rietveld was published in 
> *Acta
> Crystallographica* in 1969, having been submitted in 1968. A later paper
> published in 1969 by Rietveld alone in *Journal of Applied
> Crystallography* is the one that is always quoted and led to the name
> ‘Rietveld method’ or ‘Rietveld refinement’. Mittemeijer points out that
> this did grave injustice to the originator of the method, Bert Loopstra.
> Rietveld later left s

Re: Rietveld condamnation considered as established by some more people

[Le Bail Armel]

Bonjour Alan,My problem with the Bob van Laar and Henk Schenk paper is that it would have beencredible if signed by van Laar alone or better by Loopstra and van Laar and also ifpublished before 1980 or 1990, not in 2018.That 2018 paper looks strongly as initiated by Henk Schenk and the main argumentsinside are from old Rietveld-Schenk interferences, especially the story when Rietveld refused to plaid guilty after being accused by Schenk in a very strange manner.Now, the fact that Schenk was IUCr President may be sufficient for many people tobelieve in his version of the story. It was not sufficient for Hugo Rietveld and it is notsufficient for me.BestArmelPS - Why to insert a reference to the 1981 Pawley paper in a 1988 paper where hismethod was not used but another method much later named "Le Bail method" andbased on the Rietveld (Loopstra ??? proove it please) decomposition formula ?envoyé : 16 août 2023 à 19:08de : Alan W Hewat à : Le Bail Armel cc : "rietveld_l@ill.fr" objet : Re: Rietveld condamnation considered as established by some more peopleBonjour Armel. In answer to your question "Where did they find the text of the judgement ?" please see:"The development of powder profile refinement at the Reactor Centre Netherlands at Petten" Bob van Laar and Henk Schenkhttps://scripts.iucr.org/cgi-bin/paper?ib5058Van Laar worked at Petten with Rietveld, and Schenk was the IUCr president. This paper is apparently the basis of Mittemeijer's book. His point is that scientific discoveries are often the result of the work of many people, yet we tend to simplify the process and attribute them to individual heros. Mike Glazer is simply reviewing his book.Salutations, Alan Dr Alan Hewat, NeutronOpticsGrenoble, FRANCE (from phone)alan.he...@neutronoptics.com+33.476984168 VAT:FR79499450856http://NeutronOptics.com/hewat___   On Wed, 16 Aug 2023, 18:45 Le Bail Armel, <le-bail.ar...@orange.fr> wrote:In a book :How Science Runs – Impressions from a Scientific Career. By Eric J. MittemeijerReviewed by Mike Glazer"In another section, the author has some criticism about the famous Rietveld method in powder diffraction. He points out that the original idea for this method was put forward by Bert O. Loopstra, who later discussed the idea of whole-pattern fitting with Bob van Laar. In order to create a computer program to carry out the method, they hired the computer-savvy Hugo M. Rietveld. The first paper by Loopstra and Rietveld was published in Acta Crystallographica in 1969, having been submitted in 1968. A later paper published in 1969 by Rietveld alone in Journal of Applied Crystallography is the one that is always quoted and led to the name ‘Rietveld method’ or ‘Rietveld refinement’. Mittemeijer points out that this did grave injustice to the originator of the method, Bert Loopstra. Rietveld later left science to become a librarian: Mittemeijer says the notion that he left science because he was disappointed that the method had not found wide acceptance at the time is just a ‘fairy tale’. Thus, according to the author, the profile refinement method should more justly be called the ‘Loopstra method’, concluding that this story has a sad ending."https://www.iucr.org/news/newsletter/etc/articles?issue=156393_138339_result_page=39Where did they find the text of the judgement ? Any verdict somewhere ? Condamned by "impressions" !Any text from Loopstra who had a lot of time to tell something but never do it ?Flagged at PubPeer :https://blog.pubpeer.com/publications/79219E32306099C040C633FFABE6EChttps://blog.pubpeer.com/publications/05241C3D2890D43ED23BA1905CD32Chttps://blog.pubpeer.com/publications/9D12C10951333B68B27FB891266A88Best,Armel Le Bail++ Please do NOT attach files to the whole list  Send commands to <lists...@ill.fr> eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++ ++Please do NOT attach files to the whole list Send commands to  eg: HELP as the subject with no body textThe Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/++
++
Please do NOT attach files to the whole list 
Send commands to  eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++

Re: Rietveld condamnation considered as established by some more people

[Toby, Brian H.]

My personal feelings are that regardless of the origin of the idea, Hugo did 
the work that made crystallographic full pattern fitting possible. That 
implementation was not just a “programming task” as the minimal capabilities of 
computers of the day required significant innovation for memory and 
computational efficiency. The reasons why “Rietveld Analysis” is my preferred 
name for this technique are spelled out in chapter 4.7 of Volume H of the 
International Tables and I will not repeat them here, but I also like to draw 
additional attention to his minimally-credited method for intensity extraction, 
which was later cleverly extended into the LeBail technique. His solo 1967 
paper outlined the groundwork needed to fit all peaks in a pattern.

I was not active in the days when this work was done, and only spoke with Hugo 
twice, though we also exchanged a few e-mails, but I did have the chance to 
speak with many people who were active in CW neutron diffraction in those days. 
All were very supportive of the name "Rietveld Analysis”; none ever commented 
about to giving too much credit to Hugo. Those people included Ted Prince, who 
himself proved the statistical superiority of Rietveld Analysis over other 
approaches.

One minor update on what is below. Hugo’s original code, as published solo in 
1969, was written in Algol, but to make the technique more accessible, he 
rewrote his program in Fortran and he circulated that widely (unpublished). 
After Alan, his Fortran code went through many hands (including mine) with new 
features added from each; this is also discussed in ITH 4.7. However, GSAS was 
an all-new program in its day and did not use any of Hugo’s code.

Brian

On Aug 17, 2023, at 2:28 PM, Alan W Hewat  wrote:

Concerning the code, many, including the first versions of GSAS (and FullProf?) 
were based on the original Rietveld code that I 
modified
 at Harwell in 1972 and distributed at ILL

++
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The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++

RE: Rietveld condamnation considered as established by some more people

[Mike Glazer]

My review of Mittemeijer’s book  seems to have excited interest in the history 
of the “Rietveld” method. I, myself,  recall using Alan’s modified program 
(incorporating anisotropic displacement parameters, a welcome addition) in the 
early days and I saw that many Rietveld programs also contained this original 
code. Alan should have received much more recognition for this.

How about getting together and writing an article on the history of the program 
for the IUCr Newsletter? You could discuss the controversy there too for a 
larger audience.  The Newsletter is read by more than 13500 people, and I 
encourage including controversy.
Regards
Mike


Professor A.M. Glazer
Department of Physics
Parks Road
Oxford
OX1 3PU
Tel/Fax: 44 1865 272290
Mobile: 0778 696 0537
**
Emeritus Professor of Physics and Emeritus  Fellow of Jesus College Oxford
Visiting Professor at the University of Warwick
Crystallographer
Editor of the Newsletter of the IUCr https://www.iucr.org/news/newsletter
**
"Men will be proud to say 'I am a European'. We hope to see a day when men of 
every country will think as much of being a European as of being from their 
native land". W.Churchill, Sword Beach Memorial.

" Je ne te parlerai que cristaux" L. Pasteur (1850)
Video of my Bragg Lecture at the Royal Institution is at
https://www.youtube.com/watch?v=v9bMEUr2II4
with questions at
https://www.youtube.com/watch?v=WsPBB6azzX4



From: rietveld_l-requ...@ill.fr  On Behalf Of Alan W 
Hewat
Sent: Thursday, August 17, 2023 5:40 PM
To: Le Bail Armel 
Cc: rietveld_l@ill.fr
Subject: Re: Rietveld condamnation considered as established by some more people

Armel, it's not about you :-) But in your 1988 paper you did not reference 
Pawley (1980) and even Rietveld only appeared as #14
https://www.researchgate.net/publication/228084768_Ab_Initio_Structure_Determination_of_LiSbWO6_by_X_ray_Powder_Diffraction#fullTextFileContent

But let's not change the subject. You have published comments, linked to in 
your opening post, accusing respected scientists of "Calumny... towards a dead 
man who cannot defend himself". Simply because people who have direct 
experience of the history (which is often about dead men) do not agree with you.

And yes, Columbus did not discover America either, but he contributed. Be 
content with contributing, and let it go.

Regards Alan

Dr Alan Hewat, NeutronOptics
Grenoble, FRANCE (from phone)
alan.he...@neutronoptics.com<mailto:alan.he...@neutronoptics.com>
+33.476984168 VAT:FR79499450856
http://NeutronOptics.com/hewat
___


On Thu, 17 Aug 2023, 17:49 Le Bail Armel, 
mailto:le-bail.ar...@orange.fr>> wrote:
>And there are other examples. See this brief review of "Whole Pattern Fitting 
>- The Pawley Method" (1980) yet few people now attribute this kind of profile 
>refinement to Pawley. http://pd.chem.ucl.ac.uk/pdnn/solve1/pawley.htm

Few people ? At least me :

https://onlinelibrary.wiley.com/iucr/itc/Ha/ch3o5v0001/sec3o5o2o2o1/?

And 2168 papers cite the 1980 Pawley paper according to Google Scholar as of 
today.

Be more clear. What are exactly those other examples ?

ALB
++
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Send commands to  eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++

Re: Rietveld condamnation considered as established by some more people

[Alan W Hewat]

Dear Luca.

Since I administer the Rietveld mailing list, I could have changed the name
years ago when Van Laar and Schenk published their history, with which I
largely sympathise. I didn't, because everyone now calls it "Rietveld
Refinement", a name invented by Terry Sabine, who worked with Rietveld when
he was Australian. Rietveld himself simply called it "Profile Refinement".

For similar reasons, the country Colombo is now known as Amerigo, while
Columbo is a famous TV detective.

Concerning the code, many, including the first versions of GSAS (and
FullProf?) were based on the original Rietveld code that I modified

at
Harwell in 1972 and distributed at ILL. Armel, when he writes of his
inspiration
during long nights at ILL collecting data
 (on my instrument D1A), probably
had a version directly from Rietveld, though neither the code, nor D1A, nor
anything between Rietveld (1967,1969) and Le Bail (1987) are referenced.
Van Laar and Schenk have a brief history of how the code developed in those
"missing" 20 years https://journals.iucr.org/a/issues/2018/02/00/ib5058/

Regards Alan

Dr Alan Hewat, NeutronOptics
Grenoble, FRANCE (from phone)
alan.he...@neutronoptics.com
+33.476984168 VAT:FR79499450856
http://NeutronOptics.com/hewat
___


On Thu, 17 Aug 2023, 19:21 Luca Lutterotti, 
wrote:

> Given the involvement of Alan in the early days I would be confident to
> trust his view.
>
> So why we don't try to fix a bit the mistake. We could:
> - start renaming this list as Loopstra-Rietveld list ;-) ( I would keep
> the name Rietveld in hit, first who got the idea, second the programmer)
> - start using Loopstra-Rietveld in our papers/preentations/schools and use
> the proper references.
>
> For America, I will start calling the first who just went to the islands
> with his proper name: Cristoforo Colombo. Why do you want to change it for
> different languages?
> I would not like if they would call me Lukas Lutterottus !
>
> Finally, Alan, why we don't get a history of Loopstra-Rietveld programs?
> Speaking with different programmer I know most of them are originating
> indirectly from the Rietveld code and I think it is interesting to see how
> many are derived from others and have a root on the original code.
>
> Luca
>
> 
> [image: logo_unitrento_firma.png]
>
>
> *Luca Lutterotti*
> Dipartimento di Ingegneria Industriale
> Università di Trento
> via Sommarive, 9 - 38123 Trento (Italy)
> tel. +39 0461 2824-14 (Office), -34 (X-Ray lab)
>
> [image: ico_fb_32x32.png][image: ico_twitter_32x32.png][image:
> ico_insta_32x32.png][image: ico_linkedin_32x32.png][image:
> ico_youtube_32x32.png]
>
> Maud: http://maud.radiographema.com 
>
>
>
> On 17 Aug 2023, at 10:40, Alan W Hewat 
> wrote:
>
> Armel, it's not about you :-) But in your 1988 paper you did not reference
> Pawley (1980) and even Rietveld only appeared as #14
>
> https://www.researchgate.net/publication/228084768_Ab_Initio_Structure_Determination_of_LiSbWO6_by_X_ray_Powder_Diffraction#fullTextFileContent
>
> But let's not change the subject. You have published comments, linked to
> in your opening post, accusing respected scientists of "*Calumny...
> towards a dead man who cannot defend himself*". Simply because people who
> have direct experience of the history (which is often about dead men) do
> not agree with you.
>
> And yes, Columbus did not discover America either, but he contributed. Be
> content with contributing, and let it go.
>
> Regards Alan
> 
> Dr Alan Hewat, NeutronOptics
> Grenoble, FRANCE (from phone)
> alan.he...@neutronoptics.com
> +33.476984168 VAT:FR79499450856
> http://NeutronOptics.com/hewat 
> ___
>
>
> On Thu, 17 Aug 2023, 17:49 Le Bail Armel,  wrote:
>
>> >And there are other examples. See this brief review of "Whole Pattern
>> Fitting - The Pawley Method" (1980) yet few people now attribute this kind
>> of profile refinement to Pawley.
>> http://pd.chem.ucl.ac.uk/pdnn/solve1/pawley.htm
>>
>> Few people ? At least me :
>>
>> https://onlinelibrary.wiley.com/iucr/itc/Ha/ch3o5v0001/sec3o5o2o2o1/?
>>
>> And 2168 papers cite the 1980 Pawley paper according to Google Scholar as
>> of today.
>>
>> Be more clear. What are exactly those other examples ?
>>
>> ALB
>>
> ++
> Please do NOT attach files to the whole list  >
> Send commands to  eg: HELP as the subject with no body
> text
> The Rietveld_L list archive is on
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++
>
>
>
++
Please do NOT attach files to the whole list 

Re: Rietveld condamnation considered as established by some more people

[Luca Lutterotti]

Given the involvement of Alan in the early days I would be confident to trust 
his view.

So why we don't try to fix a bit the mistake. We could:
- start renaming this list as Loopstra-Rietveld list ;-) ( I would keep the 
name Rietveld in hit, first who got the idea, second the programmer)
- start using Loopstra-Rietveld in our papers/preentations/schools and use the 
proper references.

For America, I will start calling the first who just went to the islands with 
his proper name: Cristoforo Colombo. Why do you want to change it for different 
languages? 
I would not like if they would call me Lukas Lutterottus !

Finally, Alan, why we don't get a history of Loopstra-Rietveld programs? 
Speaking with different programmer I know most of them are originating 
indirectly from the Rietveld code and I think it is interesting to see how many 
are derived from others and have a root on the original code.

Luca

 

Luca Lutterotti
Dipartimento di Ingegneria Industriale
Università di Trento
via Sommarive, 9 - 38123 Trento (Italy)
tel. +39 0461 2824-14 (Office), -34 (X-Ray lab)




Maud: http://maud.radiographema.com 


> On 17 Aug 2023, at 10:40, Alan W Hewat  wrote:
> 
> Armel, it's not about you :-) But in your 1988 paper you did not reference 
> Pawley (1980) and even Rietveld only appeared as #14
> https://www.researchgate.net/publication/228084768_Ab_Initio_Structure_Determination_of_LiSbWO6_by_X_ray_Powder_Diffraction#fullTextFileContent
> 
> But let's not change the subject. You have published comments, linked to in 
> your opening post, accusing respected scientists of "Calumny... towards a 
> dead man who cannot defend himself". Simply because people who have direct 
> experience of the history (which is often about dead men) do not agree with 
> you. 
> 
> And yes, Columbus did not discover America either, but he contributed. Be 
> content with contributing, and let it go.
> 
> Regards Alan 
> 
> Dr Alan Hewat, NeutronOptics
> Grenoble, FRANCE (from phone)
> alan.he...@neutronoptics.com
> +33.476984168 VAT:FR79499450856
> http://NeutronOptics.com/hewat 
> ___
>
> 
> On Thu, 17 Aug 2023, 17:49 Le Bail Armel,  > wrote:
>>> >And there are other examples. See this brief review of "Whole Pattern 
>>> >Fitting - The Pawley Method" (1980) yet few people now attribute this kind 
>>> >of profile refinement to Pawley. 
>>> >http://pd.chem.ucl.ac.uk/pdnn/solve1/pawley.htm
>>> 
>>> Few people ? At least me :
>> https://onlinelibrary.wiley.com/iucr/itc/Ha/ch3o5v0001/sec3o5o2o2o1/?
>> 
>> And 2168 papers cite the 1980 Pawley paper according to Google Scholar as of 
>> today.
>> 
>> Be more clear. What are exactly those other examples ?
>> 
>> ALB
>> 
> ++
> Please do NOT attach files to the whole list 
> Send commands to  eg: HELP as the subject with no body text
> The Rietveld_L list archive is on 
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++
> 

++
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The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++

Re: Rietveld condamnation considered as established by some more people

[Alan W Hewat]

Armel, it's not about you :-) But in your 1988 paper you did not reference
Pawley (1980) and even Rietveld only appeared as #14
https://www.researchgate.net/publication/228084768_Ab_Initio_Structure_Determination_of_LiSbWO6_by_X_ray_Powder_Diffraction#fullTextFileContent

But let's not change the subject. You have published comments, linked to in
your opening post, accusing respected scientists of "*Calumny... towards a
dead man who cannot defend himself*". Simply because people who have direct
experience of the history (which is often about dead men) do not agree with
you.

And yes, Columbus did not discover America either, but he contributed. Be
content with contributing, and let it go.

Regards Alan

Dr Alan Hewat, NeutronOptics
Grenoble, FRANCE (from phone)
alan.he...@neutronoptics.com
+33.476984168 VAT:FR79499450856
http://NeutronOptics.com/hewat
___


On Thu, 17 Aug 2023, 17:49 Le Bail Armel,  wrote:

> >And there are other examples. See this brief review of "Whole Pattern
> Fitting - The Pawley Method" (1980) yet few people now attribute this kind
> of profile refinement to Pawley.
> http://pd.chem.ucl.ac.uk/pdnn/solve1/pawley.htm
>
> Few people ? At least me :
>
> https://onlinelibrary.wiley.com/iucr/itc/Ha/ch3o5v0001/sec3o5o2o2o1/?
>
> And 2168 papers cite the 1980 Pawley paper according to Google Scholar as
> of today.
>
> Be more clear. What are exactly those other examples ?
>
> ALB
>
++
Please do NOT attach files to the whole list 
Send commands to  eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++

Re: Rietveld condamnation considered as established by some more people

[Robert Gould]

It's a widespread phenomenon.  What about America being named for Vespucii
rather than Columbus?

On Thu, 17 Aug 2023, 11:49 Le Bail Armel,  wrote:

> >And there are other examples. See this brief review of "Whole Pattern
> Fitting - The Pawley Method" (1980) yet few people now attribute this kind
> of profile refinement to Pawley.
> http://pd.chem.ucl.ac.uk/pdnn/solve1/pawley.htm
>
> Few people ? At least me :
>
> https://onlinelibrary.wiley.com/iucr/itc/Ha/ch3o5v0001/sec3o5o2o2o1/?
>
> And 2168 papers cite the 1980 Pawley paper according to Google Scholar as
> of today.
>
> Be more clear. What are exactly those other examples ?
>
> ALB
> ++
> Please do NOT attach files to the whole list  >
> Send commands to  eg: HELP as the subject with no body
> text
> The Rietveld_L list archive is on
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++
>
>
++
Please do NOT attach files to the whole list 
Send commands to  eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++

Re: Rietveld condamnation considered as established by some more people

[Le Bail Armel]

>And there are other examples. See this brief review of "Whole Pattern Fitting - The Pawley Method" (1980) yet few people now attribute this kind of profile refinement to Pawley. http://pd.chem.ucl.ac.uk/pdnn/solve1/pawley.htmFew people ? At least me :https://onlinelibrary.wiley.com/iucr/itc/Ha/ch3o5v0001/sec3o5o2o2o1/?And 2168 papers cite the 1980 Pawley paper according to Google Scholar as of today.Be more clear. What are exactly those other examples ?ALB
++
Please do NOT attach files to the whole list 
Send commands to  eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++

Re: Rietveld condamnation considered as established by some more people

[Alan W Hewat]

And there are other examples. See this brief review of "Whole Pattern
Fitting - The Pawley Method" (1980) yet few people now attribute this kind
of profile refinement to Pawley.
http://pd.chem.ucl.ac.uk/pdnn/solve1/pawley.htm

On Wed, 16 Aug 2023 at 19:33,  wrote:

> Le Bail Armel schreef op 2023-08-16 18:45:
>
> In a book :
> How Science Runs – Impressions from a Scientific Career. By Eric J.
> Mittemeijer
>
>
> Reviewed by Mike Glazer
>
>
> "In another section, the author has some criticism about the famous
> Rietveld method in powder diffraction. He points out that the original idea
> for this method was put forward by Bert O. Loopstra, who later discussed
> the idea of whole-pattern fitting with Bob van Laar. In order to create a
> computer program to carry out the method, they hired the computer-savvy
> Hugo M. Rietveld. The first paper by Loopstra and Rietveld was published in 
> *Acta
> Crystallographica* in 1969, having been submitted in 1968. A later paper
> published in 1969 by Rietveld alone in *Journal of Applied
> Crystallography* is the one that is always quoted and led to the name
> ‘Rietveld method’ or ‘Rietveld refinement’. Mittemeijer points out that
> this did grave injustice to the originator of the method, Bert Loopstra.
> Rietveld later left science to become a librarian: Mittemeijer says the
> notion that he left science because he was disappointed that the method had
> not found wide acceptance at the time is just a ‘fairy tale’. Thus,
> according to the author, the profile refinement method should more justly
> be called the ‘Loopstra method’, concluding that this story has a sad
> ending."
>
>
>
> https://www.iucr.org/news/newsletter/etc/articles?issue=156393_138339_result_page=39
>
>
> Where did they find the text of the judgement ? Any verdict somewhere ?
> Condamned by "impressions" !
>
> Any text from Loopstra who had a lot of time to tell something but never
> do it ?
>
>
> Flagged at PubPeer :
>
> https://blog.pubpeer.com/publications/79219E32306099C040C633FFABE6EC
>
> https://blog.pubpeer.com/publications/05241C3D2890D43ED23BA1905CD32C
>
> https://blog.pubpeer.com/publications/9D12C10951333B68B27FB891266A88
>
>
> Best,
>
> Armel Le Bail
>
> ++
> Please do NOT attach files to the whole list  >
> Send commands to  eg: HELP as the subject with no body
> text
> The Rietveld_L list archive is on
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++
>
> Mittemeijer is not the only author who disputes the "fame" of Hugo
> Rietveld. There is a publication of Henk Schenk about the exact same topic.
> In those days it was a scandal at ECN,
>
>
> Bert Kinneging
> ++
> Please do NOT attach files to the whole list  >
> Send commands to  eg: HELP as the subject with no body
> text
> The Rietveld_L list archive is on
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++
>
>

-- 
__
Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat

__
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++

Re: Rietveld condamnation considered as established by some more people

[bertkinneging]

Le Bail Armel schreef op 2023-08-16 18:45:


In a book :

HOW SCIENCE RUNS – IMPRESSIONS FROM A SCIENTIFIC CAREER. BY ERIC J. 
MITTEMEIJER


Reviewed by Mike Glazer

"In another section, the author has some criticism about the famous 
Rietveld method in powder diffraction. He points out that the original 
idea for this method was put forward by Bert O. Loopstra, who later 
discussed the idea of whole-pattern fitting with Bob van Laar. In order 
to create a computer program to carry out the method, they hired the 
computer-savvy Hugo M. Rietveld. The first paper by Loopstra and 
Rietveld was published in _Acta Crystallographica_ in 1969, having been 
submitted in 1968. A later paper published in 1969 by Rietveld alone in 
_Journal of Applied Crystallography_ is the one that is always quoted 
and led to the name 'Rietveld method' or 'Rietveld refinement'. 
Mittemeijer points out that this did grave injustice to the originator 
of the method, Bert Loopstra. Rietveld later left science to become a 
librarian: Mittemeijer says the notion that he left science because he 
was disappointed that the method had not found wide acceptance at the 
time is just a 'fairy tale'. Thus, according to the author, the profile 
refinement method should more justly be called the 'Loopstra method', 
concluding that this story has a sad ending."


https://www.iucr.org/news/newsletter/etc/articles?issue=156393_138339_result_page=39

Where did they find the text of the judgement ? Any verdict somewhere ? 
Condamned by "impressions" !


Any text from Loopstra who had a lot of time to tell something but 
never do it ?


Flagged at PubPeer :

https://blog.pubpeer.com/publications/79219E32306099C040C633FFABE6EC

https://blog.pubpeer.com/publications/05241C3D2890D43ED23BA1905CD32C

https://blog.pubpeer.com/publications/9D12C10951333B68B27FB891266A88

Best,

Armel Le Bail
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++


Mittemeijer is not the only author who disputes the "fame" of Hugo 
Rietveld. There is a publication of Henk Schenk about the exact same 
topic. In those days it was a scandal at ECN,


Bert Kinneging++
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Re: Rietveld condamnation considered as established by some more people

[Alan W Hewat]

Bonjour Armel.

In answer to your question "Where did they find the text of the judgement
?" please see:
"The development of powder profile refinement at the Reactor Centre
Netherlands at Petten"
Bob van Laar and Henk Schenk
https://scripts.iucr.org/cgi-bin/paper?ib5058

Van Laar worked at Petten with Rietveld, and Schenk was the IUCr president.
This paper is apparently the basis of Mittemeijer's book. His point is that
scientific discoveries are often the result of the work of many people, yet
we tend to simplify the process and attribute them to individual heros.
Mike Glazer is simply reviewing his book.

Salutations, Alan

Dr Alan Hewat, NeutronOptics
Grenoble, FRANCE (from phone)
alan.he...@neutronoptics.com
+33.476984168 VAT:FR79499450856
http://NeutronOptics.com/hewat
___


On Wed, 16 Aug 2023, 18:45 Le Bail Armel,  wrote:

> In a book :
> How Science Runs – Impressions from a Scientific Career. By Eric J.
> Mittemeijer
>
>
> Reviewed by Mike Glazer
>
>
> "In another section, the author has some criticism about the famous
> Rietveld method in powder diffraction. He points out that the original idea
> for this method was put forward by Bert O. Loopstra, who later discussed
> the idea of whole-pattern fitting with Bob van Laar. In order to create a
> computer program to carry out the method, they hired the computer-savvy
> Hugo M. Rietveld. The first paper by Loopstra and Rietveld was published in 
> *Acta
> Crystallographica* in 1969, having been submitted in 1968. A later paper
> published in 1969 by Rietveld alone in *Journal of Applied
> Crystallography* is the one that is always quoted and led to the name
> ‘Rietveld method’ or ‘Rietveld refinement’. Mittemeijer points out that
> this did grave injustice to the originator of the method, Bert Loopstra.
> Rietveld later left science to become a librarian: Mittemeijer says the
> notion that he left science because he was disappointed that the method had
> not found wide acceptance at the time is just a ‘fairy tale’. Thus,
> according to the author, the profile refinement method should more justly
> be called the ‘Loopstra method’, concluding that this story has a sad
> ending."
>
>
>
> https://www.iucr.org/news/newsletter/etc/articles?issue=156393_138339_result_page=39
>
>
> Where did they find the text of the judgement ? Any verdict somewhere ?
> Condamned by "impressions" !
>
> Any text from Loopstra who had a lot of time to tell something but never
> do it ?
>
>
> Flagged at PubPeer :
>
> https://blog.pubpeer.com/publications/79219E32306099C040C633FFABE6EC
>
> https://blog.pubpeer.com/publications/05241C3D2890D43ED23BA1905CD32C
>
> https://blog.pubpeer.com/publications/9D12C10951333B68B27FB891266A88
>
>
> Best,
>
> Armel Le Bail
> ++
> Please do NOT attach files to the whole list  >
> Send commands to  eg: HELP as the subject with no body
> text
> The Rietveld_L list archive is on
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++
>
>
++
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++

Re: Rietveld website cancelled ?

[Alan Hewat]

Thanks Armel. Have a look also at the s-triazine paper. 30 years ago Pawley
and I were determining  structures of materials that are liquid at room
temperature. I remember he was worried about liquid HCN on the French
train. You might try that :-)

>From my mobile phone:
Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat

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++

Re: Rietveld website cancelled ?

[Le Bail Armel]

 

>For Armel, here are a couple of examples of automatic indexing, search-match 
>and structure DETERMINATION from neutron powder data.

 

OK, let us make a 2018 analysis of 
Pawley & Hewat (1985) Acta Ctyst. B41, 136-130.
according to 2002 criteria


sample : CF3Cl = strong chemical information

Neutron : D1A (ILL) lamda = 2.98 A

Indexing : Visser (1969) : orthorhombic cell

C-centered from systematic absences

estimation of 4 molecules per cell

A packing-analysis program written to investigate CF3Cl in Cmc21
two variables needed :
translation of the molecule along y and rotation in the yz plane

Unit cell refined using the ALLHKL (Pawley, 1981) program

Final full refinement by EDINP (Pawley, 1980)

All this fits well into the SDPD 2002 maze
http://www.cristal.org/CAC-XX/Hewat-maze.jpg

You had Pawley with you...
His packing-analysis software can be considered as a precursor
of what is called nowadays the direct-space approach, rotating
and translating a known molecule (using a grid-search approach
I presume in that case) till obtaining a good fit.

A pity that he has not solved his 1981 example for his Pawley method
(decafluorocyclohex-1-ene, C6F10) using that software (was a bit
more complex).

So, this 1985 SDPD paper cannot be considered as a good example for
a confirmation of the "structure determined by the Rietveld method"
approach. but sure it is a nice structure DETERMINATION from neutron

powder data.

 


Best

Armel

 

 

 

 

> Message du 29/08/18 12:33
> De : "Alan Hewat" 
> A : "Armel Le Bail" 
> Copie à : "rietveld_l@ill.fr" 
> Objet : Re: Rietveld website cancelled ?
> 
>
> A clear distinction having my complete agreement. (Armel)
Ouf. Nous sommes d'accord enfin :-) For Armel, here are a couple of examples of 
automatic indexing, search-match and structure DETERMINATION from neutron 
powder data. Very few citations though; crystallographers largely ignored 
neutron powder diffraction before 1987 and Hi-Tc :-)


__
>
   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE 
+33.476.98.41.68
>         http://www.NeutronOptics.com/hewat
> __



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++

Re: Rietveld website cancelled ?

[Le Bail Armel]

 

The Hugo Rietveld crucifixion is off limits. If it is not here that we can 
discuss of it, then where ?

Contrarily to you I find a good fit with religion. And vL did not use blank 
shots.

 

Armel

 

 

 

> Message du 30/08/18 13:48
> De : "Alan Hewat" 
> A : "rietveld_l@ill.fr" 
> Copie à : 
> Objet : Re: Rietveld website cancelled ?
> 
>

> You dig !
Please stop digging Armel. Loaded guns, grave digging and religion are off 
limits.


__
>
   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE 
+33.476.98.41.68
>         http://www.NeutronOptics.com/hewat
> __








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Re: Rietveld website cancelled ?

[Alan Hewat]

> You dig !
Please stop digging Armel. Loaded guns, grave digging and religion are off
limits.
__
*   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
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++

Re: Rietveld website cancelled ?

[Le Bail Armel]

Hi,

 

>It all depends on the definition


I know since a long time that it is risky to appear discussing on that 
list containing so many gurus of the Rietveld god (christened in 1978 
by Sabine and Young ; almost nobelized in 1995 ; crucified in 2018 by 
van Laar and Schenk). If god has said that his method could "determine" 
a structure, then all gurus must agree and defend the point.

But the world has changed a lot. Indeed, structure determination from
powder diffraction data has become possible. New gods appeared 30 years
ago. Rietveld is the central god in the process according to the SDPD 
maze :  http://www.cristal.org/CAC-XX/maze.jpg
However, when the SDPD whole process is described linearly, the Rietveld 
method place is not central, it is the ultimate thing to do.

Central or ultimate, this is enough apparently for the Rietveld gurus
to tell that there is only one god, their god. Then this strange 
"refinement=determination" law in their bible.

You dig !

Armel

PS - Anyway, I will continue to do my best for a resurrection, since I
recognize being one of his sons.

 

 

 

 

> Message du 29/08/18 19:00
> De : "Peter Y. Zavalij" 

> A : "% MailingList Rietveld" 
> Copie à : elb...@jhu.edu
> Objet : Re: Rietveld website cancelled ?
> 
>

It all depends on the definition. If/when we agree on the definition, there is 
usually no points for further arguing.
Anyway we could call Relieved method a structure determination from powder data 
as long as it does not included solving structure (or as David elegantly put - 
true structural solution).
Peter









Peter Y. Zavalij
Director - X-ray Crystallographic Center
University of Maryland, 
College Park, MD 20742
> 

>










>

>

On Wed, Aug 29, 2018 at 12:38 PM David Elbert  wrote:
>

Absolutely important that people understand that the Rietveld method is 
structure refinement and not solution, but as Larry points out sometimes you 
can get a more out of it if you’re clever… and have no other choice!   Here’s a 
second example:  

>
Stubbs et al., 2010, Uranyl phosphate sheet reconstruction during dehydration 
of metatorbernite [Cu(UO2)2(PO4)2·8H2O], American Mineralogist 95 (8-9): 
1132-1140 which is a bit of a brute-force approach to implying structures of 
some uranyl phosphates in a synchrotron heating experiment.  Joanne Stubbs 
sorted through known structures of related materials and used observed trends 
in refinements to select similar structures to further investigate.  Able to 
then postulate reasonable structures which then refined to the observed data 
and provided insight into this interesting group of materials.

>
Not the standard way to employment of Rietveld Refinement and certainly not 
true structural solutions, but a smart, useful, and rather satisfying 
application nonetheless.

>
Best-
David
>

>





David Elbert
> Hopkins Extreme Materials Institute
Malone Hall
> Johns Hopkins University
> 3400 N. Charles St
> Baltimore, MD 21218
> 
> (410) 516-5049
> 
> elb...@jhu.edu
> 
>

> 
> 
> 
> 
> 
>





>


On Aug 29, 2018, at 12:09 PM, Larry Finger  wrote:


On 08/29/2018 04:15 AM, Le Bail Armel wrote:
>
Hi,
> After the IUCr Monograph on Crystallography 13 (2002)
> entitled "Stucture Determination from Powder Diffraction Data"
> you may find in the preface :
> "Although the Rietveld method of structure refinement from powder
> diffraction data is often loosely considered to be synonymous with structure
> determination, it is not. The Rietveld method only comes into play in the
> final stage of the structure solution process when an approximate structural
> model has been found."
> WIF David, K Shankland, LB McCusker, C Baerlocher
> A clear distinction having my complete agreement.
> Armel
>

> Armel,
> 
> Although the above statement may be generally true, I can provide a counter 
> example. In Max W. Schmidt, Larry W. Finger, Ross J. Angel, and Robert E. 
> Dinnabier, "Synthesis, crystal structure, and phase relations of AlSiO2OH, a 
> high pressure hydrous phase", American Mineralogist, V. 83, 881-888, 1998, we 
> only had a powder - no single crystals. From data measured at ESRF, we used 
> GSAS to isolate the peaks of interest for the unknown phase, and used program 
> TREOR to autoindex the unknown and identify the impurity phases. We then 
> extracted intensities using the LeBail method, and determined the structure 
> using direct methods with program SIRPOW. The structure was then refined with 
> GSAS. We were even able to locate the H atom from Fourier maps!
> 
> Even 20 years ago, it was possible to determine the structure from X-ray 
> powder patterns.
> 
> Larry

RE: Rietveld website cancelled ?

[Le Bail Armel]

Hi Bob,

 

A kind of unique case isn't it ?

How many of such extreme examples can you list 18 years after it ? OK, some 
papers by Margiolaki, et al...

 

But the question was :

 

>As a long time practitioner of powder XRD (since 1972) I was there when the 
>superconductor craze hit in the mid-1980s.  At that time it was recognized the 
>Rietveld Method was useful only for REFINING structures which were generally 
>accepted from single crystal x-ray analysis.

>The http://www.cristal.org/rietv025/ link says the method "[allows] an 
>accurate determination of the structure."  I take that statement to mean no 
>model is required; Rietveld Analysis can determine structure without 
>preconceived model.

 

i.e. a good crystallographer, when reading "determination" thinks that no model 
is required. Then telling that the (Rietveld) method allows an accurate 
determination of the structure is misleading since that method only allows for 
a structure refinement.

 

So, a comment such as yours seems extremely out of the subject.

"a protein structure (a new insulin phase) was solved by rigid body Rietveld 
refinement"

This is a too short and strange way to present the thing. You indexed the 
pattern, guessed a model from what was already known about insulin, and had the 
chance it was good enough for the Rietveld refinement convergence. The 
determination did not included exclusively the Rietveld method, but also your 
mind and a lot of chance- congratulations.

 

You dig.

 

Armel

 

 

> Message du 29/08/18 18:26
> De : "Von Dreele, Robert B." 
> A : "Larry Finger" , "Le Bail Armel" , "Toby, Brian H." 
> Copie à : "Rietveld_L@ill.fr" 
> Objet : RE: Rietveld website cancelled ?
> 
> Hi Armel,
> A more extreme example was in Acta D56, 1549-1533 (2000) where a protein 
> structure (a new insulin phase) was solved by rigid body Rietveld refinement 
> from a synchrotron powder data set & subsequently confirmed by a single 
> crystal analysis (see Acta Cryst. (2001). D57, 1091-1100). NB: this kind of 
> thing has also happened more recently (see papers by Margiolaki, et al).
> Bob Von Dreele
> 
> -Original Message-
> From: rietveld_l-requ...@ill.fr  On Behalf Of Larry Finger
> Sent: Wednesday, August 29, 2018 11:10 AM
> To: Le Bail Armel ; Rietveld_L@ill.fr
> Subject: Re: Rietveld website cancelled ?
> 
> On 08/29/2018 04:15 AM, Le Bail Armel wrote:
> > Hi,
> > 
> > After the IUCr Monograph on Crystallography 13 (2002)
> > 
> > entitled "Stucture Determination from Powder Diffraction Data"
> > 
> > you may find in the preface :
> > 
> > "Although the Rietveld method of structure refinement from powder
> > 
> > diffraction data is often loosely considered to be synonymous with 
> > structure
> > 
> > determination, it is not. The Rietveld method only comes into play in 
> > the
> > 
> > final stage of the structure solution process when an approximate 
> > structural
> > 
> > model has been found."
> > 
> > WIF David, K Shankland, LB McCusker, C Baerlocher
> > 
> > A clear distinction having my complete agreement.
> > 
> > Armel
> 
> Armel,
> 
> Although the above statement may be generally true, I can provide a counter 
> example. In Max W. Schmidt, Larry W. Finger, Ross J. Angel, and Robert E. 
> Dinnabier, "Synthesis, crystal structure, and phase relations of AlSiO2OH, a 
> high pressure hydrous phase", American Mineralogist, V. 83, 881-888, 1998, we 
> only had a powder - no single crystals. From data measured at ESRF, we used 
> GSAS to isolate the peaks of interest for the unknown phase, and used program 
> TREOR to autoindex the unknown and identify the impurity phases. We then 
> extracted intensities using the LeBail method, and determined the structure 
> using direct methods with program SIRPOW. The structure was then refined with 
> GSAS. We were even able to locate the H atom from Fourier maps!
> 
> Even 20 years ago, it was possible to determine the structure from X-ray 
> powder patterns.
> 
> Larry
> 
> 
>++
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++

Re: Rietveld website cancelled ?

[Kurt Leinenweber]

Was that Clint Eastwood?  - Kurt


From: rietveld_l-requ...@ill.fr  on behalf of Le 
Bail Armel 
Sent: Wednesday, August 29, 2018 12:01:25 PM
To: Rietveld_L@ill.fr
Subject: Re: Rietveld website cancelled ?


OK, seems that the SDPD book preface looks unclear to some.



Western movies adepts well know that sentence :

"You see, in this world there's two kinds of people, my friend: those with 
loaded guns, and those who dig. You dig. .."



Similarly, there are two kinds of people, those believing that the sense of the 
words "structure determination" and

"structure refinement" are the same, and the others. You dig.



Best



Armel









> Message du 29/08/18 18:09
> De : "Larry Finger" 
> A : "Le Bail Armel" , Rietveld_L@ill.fr
> Copie à :
> Objet : Re: Rietveld website cancelled ?
>
> On 08/29/2018 04:15 AM, Le Bail Armel wrote:
> > Hi,
> >
> > After the IUCr Monograph on Crystallography 13 (2002)
> >
> > entitled "Stucture Determination from Powder Diffraction Data"
> >
> > you may find in the preface :
> >
> > "Although the Rietveld method of structure refinement from powder
> >
> > diffraction data is often loosely considered to be synonymous with structure
> >
> > determination, it is not. The Rietveld method only comes into play in the
> >
> > final stage of the structure solution process when an approximate structural
> >
> > model has been found."
> >
> > WIF David, K Shankland, LB McCusker, C Baerlocher
> >
> > A clear distinction having my complete agreement.
> >
> > Armel
>
> Armel,
>
> Although the above statement may be generally true, I can provide a counter
> example. In Max W. Schmidt, Larry W. Finger, Ross J. Angel, and Robert E.
> Dinnabier, "Synthesis, crystal structure, and phase relations of AlSiO2OH, a
> high pressure hydrous phase", American Mineralogist, V. 83, 881-888, 1998, we
> only had a powder - no single crystals. From data measured at ESRF, we used 
> GSAS
> to isolate the peaks of interest for the unknown phase, and used program TREOR
> to autoindex the unknown and identify the impurity phases. We then extracted
> intensities using the LeBail method, and determined the structure using direct
> methods with program SIRPOW. The structure was then refined with GSAS. We were
> even able to locate the H atom from Fourier maps!
>
> Even 20 years ago, it was possible to determine the structure from X-ray 
> powder
> patterns.
>
> Larry
>
>
>
++
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++

Re: Rietveld website cancelled ?

[Larry Finger]

On 08/29/2018 02:01 PM, Le Bail Armel wrote:

OK, seems that the SDPD book preface looks unclear to some.

Western movies adepts well know that sentence :

"You see, in this world there's /two kinds/ of /people/, my friend: /those/ with 
loaded /guns/, and /those/ who /dig/. /You dig/. .."


Similarly, there are two kinds of people, those believing that the sense of the 
words "structure determination" and


"structure refinement" are the same, and the others. You dig.


I am happy to have been one of the "others". I also know the difference between 
lattice and structure. :)


Larry

++
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++

Re: Rietveld website cancelled ?

[Le Bail Armel]

OK, seems that the SDPD book preface looks unclear to some.

 

Western movies adepts well know that sentence :

"You see, in this world there's two kinds of people, my friend: those with 
loaded guns, and those who dig. You dig. .."

 

Similarly, there are two kinds of people, those believing that the sense of the 
words "structure determination" and


"structure refinement" are the same, and the others. You dig.


 

Best


 

Armel


 

 

 

 

> Message du 29/08/18 18:09
> De : "Larry Finger" 
> A : "Le Bail Armel" , Rietveld_L@ill.fr
> Copie à : 
> Objet : Re: Rietveld website cancelled ?
> 
> On 08/29/2018 04:15 AM, Le Bail Armel wrote:
> > Hi,
> > 
> > After the IUCr Monograph on Crystallography 13 (2002)
> > 
> > entitled "Stucture Determination from Powder Diffraction Data"
> > 
> > you may find in the preface :
> > 
> > "Although the Rietveld method of structure refinement from powder
> > 
> > diffraction data is often loosely considered to be synonymous with structure
> > 
> > determination, it is not. The Rietveld method only comes into play in the
> > 
> > final stage of the structure solution process when an approximate structural
> > 
> > model has been found."
> > 
> > WIF David, K Shankland, LB McCusker, C Baerlocher
> > 
> > A clear distinction having my complete agreement.
> > 
> > Armel
> 
> Armel,
> 
> Although the above statement may be generally true, I can provide a counter 
> example. In Max W. Schmidt, Larry W. Finger, Ross J. Angel, and Robert E. 
> Dinnabier, "Synthesis, crystal structure, and phase relations of AlSiO2OH, a 
> high pressure hydrous phase", American Mineralogist, V. 83, 881-888, 1998, we 
> only had a powder - no single crystals. From data measured at ESRF, we used 
> GSAS 
> to isolate the peaks of interest for the unknown phase, and used program 
> TREOR 
> to autoindex the unknown and identify the impurity phases. We then extracted 
> intensities using the LeBail method, and determined the structure using 
> direct 
> methods with program SIRPOW. The structure was then refined with GSAS. We 
> were 
> even able to locate the H atom from Fourier maps!
> 
> Even 20 years ago, it was possible to determine the structure from X-ray 
> powder 
> patterns.
> 
> Larry
> 
> 
>++
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Re: Rietveld website cancelled ?

[Peter Y. Zavalij]

It all depends on the definition. If/when we agree on the definition, there
is usually no points for further arguing.
Anyway we could call Relieved method a structure determination from powder
data as long as it does not included solving structure (or as David
elegantly put - true structural solution).
Peter

Peter Y. Zavalij
Director - X-ray Crystallographic Center
University of Maryland,
College Park, MD 20742



On Wed, Aug 29, 2018 at 12:38 PM David Elbert  wrote:

> Absolutely important that people understand that the Rietveld method is
> structure refinement and not solution, but as Larry points out sometimes
> you can get a more out of it if you’re clever… and have no other choice!
> Here’s a second example:
>
> Stubbs et al., 2010, Uranyl phosphate sheet reconstruction during
> dehydration of metatorbernite [Cu(UO2)2(PO4)2·8H2O], American
> Mineralogist 95 (8-9): 1132-1140 which is a bit of a brute-force approach
> to implying structures of some uranyl phosphates in a synchrotron heating
> experiment.  Joanne Stubbs sorted through known structures of related
> materials and used observed trends in refinements to select similar
> structures to further investigate.  Able to then postulate reasonable
> structures which then refined to the observed data and provided insight
> into this interesting group of materials.
>
> Not the standard way to employment of Rietveld Refinement and certainly
> not true structural solutions, but a smart, useful, and rather satisfying
> application nonetheless.
>
> Best-
> David
>
> David Elbert
> Hopkins Extreme Materials Institute
> Malone Hall
> Johns Hopkins University
> 3400 N. Charles St
> Baltimore, MD 21218
>
> (410) 516-5049
>
> elb...@jhu.edu
>
>
>
>
>
>
>
>
> On Aug 29, 2018, at 12:09 PM, Larry Finger 
> wrote:
>
> On 08/29/2018 04:15 AM, Le Bail Armel wrote:
>
> Hi,
> After the IUCr Monograph on Crystallography 13 (2002)
> entitled "Stucture Determination from Powder Diffraction Data"
> you may find in the preface :
> "Although the Rietveld method of structure refinement from powder
> diffraction data is often loosely considered to be synonymous with
> structure
> determination, it is not. The Rietveld method only comes into play in the
> final stage of the structure solution process when an approximate
> structural
> model has been found."
> WIF David, K Shankland, LB McCusker, C Baerlocher
> A clear distinction having my complete agreement.
> Armel
>
>
> Armel,
>
> Although the above statement may be generally true, I can provide a
> counter example. In Max W. Schmidt, Larry W. Finger, Ross J. Angel, and
> Robert E. Dinnabier, "Synthesis, crystal structure, and phase relations of
> AlSiO2OH, a high pressure hydrous phase", American Mineralogist, V. 83,
> 881-888, 1998, we only had a powder - no single crystals. From data
> measured at ESRF, we used GSAS to isolate the peaks of interest for the
> unknown phase, and used program TREOR to autoindex the unknown and identify
> the impurity phases. We then extracted intensities using the LeBail method,
> and determined the structure using direct methods with program SIRPOW. The
> structure was then refined with GSAS. We were even able to locate the H
> atom from Fourier maps!
>
> Even 20 years ago, it was possible to determine the structure from X-ray
> powder patterns.
>
> Larry
>
>
> ++
> Please do NOT attach files to the whole list  >
> Send commands to  eg: HELP as the subject with no body
> text
> The Rietveld_L list archive is on
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++
>
>
> ++
> Please do NOT attach files to the whole list  >
> Send commands to  eg: HELP as the subject with no body
> text
> The Rietveld_L list archive is on
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++
>
>
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RE: Rietveld website cancelled ?

[Von Dreele, Robert B.]

Hi Armel,
A more extreme example was in Acta D56, 1549-1533 (2000) where a protein 
structure (a new insulin phase) was solved by rigid body Rietveld refinement 
from a synchrotron powder data set & subsequently confirmed by a single crystal 
analysis (see Acta Cryst. (2001). D57, 1091-1100). NB: this kind of thing has 
also happened more recently (see papers by Margiolaki, et al).
Bob Von Dreele

-Original Message-
From: rietveld_l-requ...@ill.fr  On Behalf Of Larry 
Finger
Sent: Wednesday, August 29, 2018 11:10 AM
To: Le Bail Armel ; Rietveld_L@ill.fr
Subject: Re: Rietveld website cancelled ?

On 08/29/2018 04:15 AM, Le Bail Armel wrote:
> Hi,
> 
> After the IUCr Monograph on Crystallography 13 (2002)
> 
> entitled "Stucture Determination from Powder Diffraction Data"
> 
> you may find in the preface :
> 
> "Although the Rietveld method of structure refinement from powder
> 
> diffraction data is often loosely considered to be synonymous with 
> structure
> 
> determination, it is not. The Rietveld method only comes into play in 
> the
> 
> final stage of the structure solution process when an approximate 
> structural
> 
> model has been found."
> 
> WIF David, K Shankland, LB McCusker, C Baerlocher
> 
> A clear distinction having my complete agreement.
> 
> Armel

Armel,

Although the above statement may be generally true, I can provide a counter 
example. In Max W. Schmidt, Larry W. Finger, Ross J. Angel, and Robert E. 
Dinnabier, "Synthesis, crystal structure, and phase relations of AlSiO2OH, a 
high pressure hydrous phase", American Mineralogist, V. 83, 881-888, 1998, we 
only had a powder - no single crystals. From data measured at ESRF, we used 
GSAS to isolate the peaks of interest for the unknown phase, and used program 
TREOR to autoindex the unknown and identify the impurity phases. We then 
extracted intensities using the LeBail method, and determined the structure 
using direct methods with program SIRPOW. The structure was then refined with 
GSAS. We were even able to locate the H atom from Fourier maps!

Even 20 years ago, it was possible to determine the structure from X-ray powder 
patterns.

Larry


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Re: Rietveld website cancelled ?

[Larry Finger]

On 08/29/2018 04:15 AM, Le Bail Armel wrote:

Hi,

After the IUCr Monograph on Crystallography 13 (2002)

entitled "Stucture Determination from Powder Diffraction Data"

you may find in the preface :

"Although the Rietveld method of structure refinement from powder

diffraction data is often loosely considered to be synonymous with structure

determination, it is not. The Rietveld method only comes into play in the

final stage of the structure solution process when an approximate structural

model has been found."

WIF David, K Shankland, LB McCusker, C Baerlocher

A clear distinction having my complete agreement.

Armel


Armel,

Although the above statement may be generally true, I can provide a counter 
example. In Max W. Schmidt, Larry W. Finger, Ross J. Angel, and Robert E. 
Dinnabier, "Synthesis, crystal structure, and phase relations of AlSiO2OH, a 
high pressure hydrous phase", American Mineralogist, V. 83, 881-888, 1998, we 
only had a powder - no single crystals. From data measured at ESRF, we used GSAS 
to isolate the peaks of interest for the unknown phase, and used program TREOR 
to autoindex the unknown and identify the impurity phases. We then extracted 
intensities using the LeBail method, and determined the structure using direct 
methods with program SIRPOW. The structure was then refined with GSAS. We were 
even able to locate the H atom from Fourier maps!


Even 20 years ago, it was possible to determine the structure from X-ray powder 
patterns.


Larry


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Re: Rietveld website cancelled ?

[Le Bail Armel]

 

>Very few citations though;

 

The fact is that you don't cite this couple of examples in your own list of 
selected publications :

http://hewat.net/science/

If you find them of poor interest, the World follows you.

 

Armel

 

PS - A positive search-match (using the COD) signifies that the structure is 
already determined (not always if you use ICDD), then if you wish, you may 
refine it by the Rietveld method

 

 

> Message du 29/08/18 12:35
> De : "Alan Hewat" 
> A : "Armel Le Bail" 
> Copie à : "rietveld_l@ill.fr" 
> Objet : Re: Rietveld website cancelled ?
> 
>
> A clear distinction having my complete agreement. (Armel)
Ouf. Nous sommes d'accord enfin :-) For Armel, here are a couple of examples of 
automatic indexing, search-match and structure DETERMINATION from neutron 
powder data. Very few citations though; crystallographers largely ignored 
neutron powder diffraction before 1987 and Hi-Tc :-)


__
>
   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE 
+33.476.98.41.68
>         http://www.NeutronOptics.com/hewat
> __






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Re: Rietveld website cancelled ?

[Alan Hewat]

> A clear distinction having my complete agreement. (Armel)
Ouf. Nous sommes d'accord enfin :-) For Armel, here are a couple of examples

of automatic indexing, search-match and structure DETERMINATION from
neutron powder data. Very few citations though; crystallographers largely
ignored neutron powder diffraction before 1987 and Hi-Tc :-)
__
*   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
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RE: Rietveld website cancelled ?

[Le Bail Armel]

Hi,

 

After the IUCr Monograph on Crystallography 13 (2002)

entitled "Stucture Determination from Powder Diffraction Data"

you may find in the preface :

"Although the Rietveld method of structure refinement from powder

diffraction data is often loosely considered to be synonymous with structure

determination, it is not. The Rietveld method only comes into play in the

final stage of the structure solution process when an approximate structural

model has been found."

WIF David, K Shankland, LB McCusker, C Baerlocher

 

A clear distinction having my complete agreement.

 

Armel

http://www.cristal.org/CAC-XX/maze.jpg

http://www.cristal.org/CAC-XX/Rietveld.ppt

 

 

> Message du 29/08/18 10:14
> De : "May, Frank" 
> A : "Alan Hewat" , "rietveld_l@ill.fr" 
> Copie à : 
> Objet : RE: Rietveld website cancelled ?
> 
> To all:
> 
> Initially I sent this to Alan who suggested I open discussion to the entire 
> community. I've posted similar in past years and have been FLAMED. Please 
> keep it civil. ;-)
> =
> As a long time practitioner of powder XRD (since 1972) I was there when the 
> superconductor craze hit in the mid-1980s. At that time it was recognized the 
> Rietveld Method was useful only for REFINING structures which were generally 
> accepted from single crystal x-ray analysis.
> 
> The http://www.cristal.org/rietv025/ link says the method "[allows] an 
> accurate determination of the structure." I take that statement to mean no 
> model is required; Rietveld Analysis can determine structure without 
> preconceived model.
> 
> Thanks for reading.
> 
> Blessings from toasty and warm St. Louis, MO.
> 
> Frank May
> Research Investigator
> University of Missouri-St. Louis
> 
> formerly at Monsanto Company (which recently became part of 
> BAYER)++
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> ++
> 
>++
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RE: Rietveld website cancelled ?

[May, Frank]

To all:

Initially I sent this to Alan who suggested I open discussion to the entire 
community.  I've posted similar in past years and have been FLAMED.  Please 
keep it civil.  ;-)
=
As a long time practitioner of powder XRD (since 1972) I was there when the 
superconductor craze hit in the mid-1980s.  At that time it was recognized the 
Rietveld Method was useful only for REFINING structures which were generally 
accepted from single crystal x-ray analysis.

The http://www.cristal.org/rietv025/ link says the method "[allows] an accurate 
determination of the structure."  I take that statement to mean no model is 
required; Rietveld Analysis can determine structure without preconceived model.

Thanks for reading.

Blessings from toasty and warm St. Louis, MO.

Frank May
Research Investigator
University of Missouri-St. Louis

formerly at Monsanto Company (which recently became part of BAYER)++
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Re: Rietveld website cancelled ?

[Alan Hewat]

Good work Armel. Note that little is lost once it is posted to the WWW,
since it is backed up in several places. The "WayBack Machine" is a good
way of recovering historic web sites. The WayBack server is a bit slow,
since it is supported only by donations and is probably in heavy demand -
see:
https://web.archive.org/web/20180212154506/http://home.wxs.nl/~rietv025/

On Tue, 28 Aug 2018 at 17:15, Le Bail Armel  wrote:

>
>
> http://home.wxs.nl/~rietv025/
>
> It has suddenly disappeared a few days ago.
>
>
>
> A copy can be found here :
>
> http://www.cristal.org/rietv025/
>
>
>
> Armel
>
>
>
>
>
>
>
>
> ++
> Please do NOT attach files to the whole list  >
> Send commands to  eg: HELP as the subject with no body
> text
> The Rietveld_L list archive is on
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++
>
>

-- 
__
*   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
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Re: Rietveld

[Alan Hewat]

*>  Argh ! Shame on us three ! *
Yes, we went too far. Sorry Armel. But Robert only has to read the footer
at the bottom of every post to find how to remove himself.
__
*   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
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Re: Rietveld

[Le Bail Armel]

Argh ! Shame on us three !

 

But be careful to not confuse an example with a counter-example ;-)

 

In 1986 had already started the times where Rietveld was so famous that giving 
his name in the paper was sufficient. You can probably find >20.000 such papers 
citing the Rietveld method and not his 1967 or 1969 papers. Rietveld's real 
number of citations is probably closer to >40.000 than to 15.000. But you know 
that already...

 

Best,

 

Armel

 

 

 

 

> Message du 22/08/18 14:23
> De : "Alan Hewat" 
> A : "rietveld_l@ill.fr" 
> Copie à : 
> Objet : Re: Rietveld
> 
>

> Another example.. Loopstra, van Laar and Breed Physics Letters 26A(11) 1968, 
> 526 (AleB)

>
Examples are easy. In Gibaud, Le Bail and Bulou J. Phys. C: Solid State Phys. 
19 (1986) 4623
"...the Rietveld program modified by Le Bail (1985)" is used to refine data 
collected at ILL on D1A (Hewat & Bailey 1976) without citing either Rietveld or 
the people who built the diffractometer, helped with the data collection, and 
supplied the 1972 Rietveld code. 

__
>
   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE 
+33.476.98.41.68
>         http://www.NeutronOptics.com/hewat
> __





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Re: Rietveld

[Alan Hewat]

*> Another example.. Loopstra, van Laar and Breed Physics Letters 26A(11)
1968, 526* (AleB)

Examples are easy. In Gibaud, Le Bail and Bulou
 J.
Phys. C: Solid State Phys. 19 (1986) 4623
"*...the Rietveld program modified by Le Bail (1985)*" is used to refine
data collected at ILL on D1A (Hewat & Bailey 1976
)
without citing either Rietveld or the people who built the diffractometer,
helped with the data collection, and supplied the 1972 Rietveld code
.
__
*   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
++
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++

[SUSPECTED SPAM] Re: Rietveld

[Leonid Solovyov]

>That is why I prefer to use Rietveld's original term "profile refinement" for 
>all kinds of powder pattern refinement, and reference Loopstra and Rietveld 
>(1969) instead of >just Rietveld (1969)

In the Introduction of Loopstra and Rietveld (1969) they referred to the 
approach as "the profile refinement technique (Rietveld, 1967, 1968)" and give 
some important expressions for the refinement procedure that were absent in 
Rietveld (1967). So, a more correct citation for the profile refinement 
technique would be (Rietveld, 1967, Loopstra & Rietveld, 1969).


***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
*** 

On Wednesday, August 22, 2018, 3:02:48 PM GMT+7, Alan Hewat 
 wrote:  
 
 Leonid. Rietveld's code is indeed a specific type of profile refinement. 
Structure parameters are refined to fit the observed profile intensities using 
a least squares code similar to that used to fit integrated Bragg intensities 
at Oak Ridge - ORFLS (1962). From 1961 profile refinement methods were used at 
Argonne to fit multiple peaks to profile intensities, and later at Petten. All 
references are given in  vL
Unfortunately, the term "Rietveld method" has been applied to types of profile 
refinement that are closer to earlier profile refinement methods, such as 
refining the proportions of different phases where the individual structures 
are known.
That is why I prefer to use Rietveld's original term "profile refinement" for 
all kinds of powder pattern refinement, and reference Loopstra and Rietveld 
(1969) instead of just Rietveld (1969). I would also call quantitative phase 
analysis from powders "profile refinement" rather than Rietveld refinement, and 
reference Werner et al. (1979).
__
   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE 
  from my tablet
 +33.476.98.41.68
        http://www.NeutronOptics.com/hewat
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Re: Rietveld

[Alan Hewat]

Leonid. Rietveld's code is indeed a specific type of profile refinement.
Structure parameters are refined to fit the observed profile intensities
using a least squares code similar to that used to fit integrated Bragg
intensities at Oak Ridge - ORFLS (1962). From 1961 profile refinement
methods were used at Argonne to fit multiple peaks to profile intensities,
and later at Petten. All references are given in  vL
.

Unfortunately, the term "Rietveld method" has been applied to types of
profile refinement that are closer to earlier profile refinement methods,
such as refining the proportions of different phases where the individual
structures are known.

That is why I prefer to use Rietveld's original term "profile refinement"
for all kinds of powder pattern refinement, and reference Loopstra and
Rietveld (1969) instead of just Rietveld (1969). I would also call
quantitative phase analysis from powders "profile refinement" rather than
Rietveld refinement, and reference Werner et al. (1979).
__
   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE
  from my tablet
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
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Re: Rietveld

[Leonid Solovyov]

>Gauss and Legendre's work shows that science is not performed by individuals 
>in a vacuum. >Now we call it "Least Squares Refinement" and not "Gauss 
>Refinement".

It seems that the basic collision is in the absence of strict and commonly 
accepted definition of the 'Rietveld Method' term. Does the Rietveld method 
imply:
1) a general concept of structure refinement using powder data in their 
original form of scanned profile,
or

 2) just one (of many possible) specific realization of this concept as a least 
squares optimization of weighted profile difference?
I'd prefer the second variant, which may also help resolving the issue of 
credits and citations.


***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
*** 

On Wednesday, August 22, 2018, 11:52:03 AM GMT+7, Alan Hewat 
 wrote:  
 
 >  credit should be given to Rietveld for developing and distributing his 
 >software No-one is disputing that, even if Rietveld himself never gave credit 
 >to anyone else. In Rietveld (1969) he merely `thanks Drs B. O. Loopstra and 
 >B. van Laar for their suggestions and helpful criticism'. Yet according to 
 >vL he had been hired as a postdoc to contribute to a problem they had been 
 >working on.. His home page is an extreme example, where others are only 
 >credited for their hommage to him. 
Gauss and Legendre's work shows that science is not performed by individuals in 
a vacuum. Now we call it "Least Squares Refinement" and not "Gauss Refinement".
__
   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE 
 +33.476.98.41.68
        http://www.NeutronOptics.com/hewat
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Re: Rietveld

[Alan Hewat]

*>   credit should be given to Rietveld for developing and distributing his
software *
No-one is disputing that, even if Rietveld himself never gave credit to
anyone else. In Rietveld (1969) he merely `*thanks Drs B. O. Loopstra and
B. van Laar for their suggestions and helpful criticism*'. Yet according to
vL  he had been
hired as a postdoc to contribute to a problem they had been working on..
His home page  is an extreme example, where
others are only credited for their hommage to him.

Gauss and Legendre's work shows that science is not performed by
individuals in a vacuum.
*Now we call it "Least Squares Refinement" and not "Gauss Refinement".*
__
*   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
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RE: Rietveld

[AlanCoelho]

It seems that even the origin of least squares is debateable:

 

https://blog.bookstellyouwhy.com/carl-friedrich-gauss-and-the-method-of-least-squares
 

 

"That Gauss was the first to define the method of least squares was contested 
in his day. Adrien-Marie Legendre first published a version of the method in 
1805"

 

I though this discussion would divide the community but from Armel’s pole (good 
idea) it hasn’t. 

 

The Rietveld method is an implementation of the method of least squares with 
the function being minimized changed to suite powder diffraction. Looking at 
the least squares formulae as defined by Gauss, Eq. (1) at:

 

https://books.google.com.au/books?id=gtoTkL7heS0C 
<https://books.google.com.au/books?id=gtoTkL7heS0C=RA1-PA193=RA1-PA193=Charles+fredrick+gauss+and+non-linear+least+squares=bl=ZAS84VXPuo=CZR3HPkPEEY4sxMfCHerAako3qQ=en=X=2ahUKEwj-i6PGt_rcAhWBM94KHbt_AZMQ6AEwAnoECAgQAQ#v=onepage=Charles%20fredrick%20gauss%20and%20non-linear%20least%20squares=false>
 
=RA1-PA193=RA1-PA193=Charles+fredrick+gauss+and+non-linear+least+squares=bl=ZAS84VXPuo=CZR3HPkPEEY4sxMfCHerAako3qQ=en=X=2ahUKEwj-i6PGt_rcAhWBM94KHbt_AZMQ6AEwAnoECAgQAQ#v=onepage=Charles%20fredrick%20gauss%20and%20non-linear%20least%20squares=false

 

or at:

 

https://en.wikipedia.org/wiki/Least_squares

 

we see that it is familiar except that f describes a diffraction pattern. 
Fitting to the powder data itself (rather than first performing data reduction 
in the form of extracting intensities) is what is implied by Gauss and it seems 
odd that this was not considered by many. 

 

Also, computer code for performing least squares on powder data is 70% 
identical (in my estimate) to performing least squares on single crystal data. 
In fact, if only Gaussian peak shapes are considered then its 90% identical. I 
should know as computer code that perform derivatives on structural parameters 
for single crystal data are exactly the same code used to perform derivatives 
on powder data.

 

My feelings are similar to Scott Speakman in that credit should be given to 
Rietveld for developing and distributing his software; if more was done by 
Rietveld in regards to developing f then all the better.

 

All the best

Alan Coelho

 

 

From: rietveld_l-requ...@ill.fr  On Behalf Of Scott 
Speakman
Sent: Wednesday, 22 August 2018 4:35 AM
To: Rietveld_l@ill.fr
Subject: RE: Rietveld

 

It is interesting to read this conversation and to hear the various points of 
view. 

 

I have one point for consideration to add, and would love to hear the opinion 
of those who were more closely involved in those early days:  I was always 
under the impression that the nomenclature "Rietveld technique" evolved mostly 
because Hugo Rietveld freely distributed the programming code for others to 
use, and allowed the code to be used and incorporated into other programs 
without ever requesting licensing fees or the like.  In that case, the name 
"Rietveld technique" isn't used to credit the inventor(s) of the methodology, 
but rather to acknowledge the author of the original programming code.  

 

 


Kind Regards,

Scott A Speakman, Ph.D.
Principal Scientist- XRD


Tel
Mob

+1 800 279 7297
+1 508 361 8121



Malvern Panalytical Inc.
117 Flanders Road
Westborough MA 01581
United States

 <mailto://scott.speak...@panalytical.com> scott.speak...@panalytical.com
 <http://www.malvernpanalytical.com> www.malvernpanalytical.com


 


This email and any files transmitted with it are confidential and maybe legally 
privileged. Such message is intended solely for the use of the individual or 
entity to whom they are addressed. Please notify the originator of the message 
if you are not the intended recipient and destroy all copies of the message. 
Please note that any use, dissemination, or reproduction is strictly prohibited 
and may be unlawful. 



The way we want to do business:  <http://www.spectrisethics.co.uk/MAL/> The 
value of Integrity - Code of Business Ethics

 

From: rietveld_l-requ...@ill.fr <mailto:rietveld_l-requ...@ill.fr>  
mailto:rietveld_l-requ...@ill.fr> > On Behalf Of Le 
Bail Armel
Sent: Tuesday, August 21, 2018 11:09 AM
To: Rietveld_l@ill.fr <mailto:Rietveld_l@ill.fr> 
Subject: Re: Rietveld

 

The >1500 subscribers can vote... :

 

https://doodle.com/poll/gh3v3nfhue599w23

 

Best,

 

Armel

 

 

 

> Message du 21/08/18 19:10
> De : "Alan Hewat"  <mailto:alan.he...@neutronoptics.com> >
> A : "rietveld_l@ill.fr <mailto:rietveld_l@ill.fr> "  <mailto:Rietveld_l@ill.fr> >
> Copie à : 
> Objet : Re: Rietveld
> 
> 

> As a matter of course we didn't took part in the discussion... (Schenk) 

> ...people pretending now to speak in place of Loopstra should stop to do so 
> (Le Bail)

What a contrast of style and substance. Late believers are true believers,

Re: Rietveld

[Alan Hewat]

Scott. If for commercial reasons you don't wish to disclose the details of
Panalytical's code,  I suggest you reference "code based on the Rietveld
code - Rietveld (1969) Reactor Centrum Nederland Report RCN-104 (which
contains the original code).  My version is on:
http://www.ccp14.ac.uk/ccp/web-mirrors/hewat-rietveld/
__
*   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
++
Please do NOT attach files to the whole list 
Send commands to  eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++

Re: Rietveld

[Alan Hewat]

Scott. If you use the code distributed by Rietveld, you should certainly
acknowledge it as "the Rietveld program/code" as I did in my Harwell
report  1973_The_Rietveld_Program_for_the_Profile_Refinement_of_
Neutron_Diffraction_Powder_Patterns_AERE_R7350-von_Dreele_annotations.pdf



In that case you should also list the actual code you use, as I did. Alan.

On Tue, 21 Aug 2018 at 20:36, Scott Speakman 
wrote:

> It is interesting to read this conversation and to hear the various points
> of view.
>
>
>
> I have one point for consideration to add, and would love to hear the
> opinion of those who were more closely involved in those early days:  I was
> always under the impression that the nomenclature "Rietveld technique"
> evolved mostly because Hugo Rietveld freely distributed the programming
> code for others to use, and allowed the code to be used and incorporated
> into other programs without ever requesting licensing fees or the like.  In
> that case, the name "Rietveld technique" isn't used to credit the
> inventor(s) of the methodology, but rather to acknowledge the author of the
> original programming code.
>
>
>
>
>
>
> Kind Regards,
>
>
> *Scott A Speakman, Ph.D. *Principal Scientist- XRD
>
__
*   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
++
Please do NOT attach files to the whole list 
Send commands to  eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++

RE: Rietveld

[Scott Speakman]

It is interesting to read this conversation and to hear the various points of 
view.

I have one point for consideration to add, and would love to hear the opinion 
of those who were more closely involved in those early days:  I was always 
under the impression that the nomenclature "Rietveld technique" evolved mostly 
because Hugo Rietveld freely distributed the programming code for others to 
use, and allowed the code to be used and incorporated into other programs 
without ever requesting licensing fees or the like.  In that case, the name 
"Rietveld technique" isn't used to credit the inventor(s) of the methodology, 
but rather to acknowledge the author of the original programming code.



Kind Regards,

Scott A Speakman, Ph.D.
Principal Scientist- XRD


Tel
Mob

+1 800 279 7297
+1 508 361 8121


Malvern Panalytical Inc.
117 Flanders Road
Westborough MA 01581
United States

scott.speak...@panalytical.com<mailto://scott.speak...@panalytical.com>
www.malvernpanalytical.com<http://www.malvernpanalytical.com>



This email and any files transmitted with it are confidential and maybe legally 
privileged. Such message is intended solely for the use of the individual or 
entity to whom they are addressed. Please notify the originator of the message 
if you are not the intended recipient and destroy all copies of the message. 
Please note that any use, dissemination, or reproduction is strictly prohibited 
and may be unlawful.


The way we want to do business: The value of Integrity - Code of Business 
Ethics<http://www.spectrisethics.co.uk/MAL/>


From: rietveld_l-requ...@ill.fr  On Behalf Of Le 
Bail Armel
Sent: Tuesday, August 21, 2018 11:09 AM
To: Rietveld_l@ill.fr
Subject: Re: Rietveld


The >1500 subscribers can vote... :



https://doodle.com/poll/gh3v3nfhue599w23



Best,



Armel






> Message du 21/08/18 19:10
> De : "Alan Hewat" 
> mailto:alan.he...@neutronoptics.com>>
> A : "rietveld_l@ill.fr<mailto:rietveld_l@ill.fr>" 
> mailto:Rietveld_l@ill.fr>>
> Copie à :
> Objet : Re: Rietveld
>
>
> As a matter of course we didn't took part in the discussion... (Schenk)
> ...people pretending now to speak in place of Loopstra should stop to do so 
> (Le Bail)
What a contrast of style and substance. Late believers are true believers, and 
Passion evicts Doubt.
>

>
Seeking sanity, I refer back to Miguel and the meaning of truth and knowledge.:
>
> Scientists cannot ask anyone for the absolute truth  (A consideration valid 
> for one but also for two)
> By 
> absolute<https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.google.fr%2Fsearch%3Fq%3Dabsolute=01%7C01%7Cscott.speakman%40panalytical.com%7C04af11f1491744c1a66108d607916d9c%7C071061f3d56946889edeb63a6a7f1ecc%7C0=S6uop0uy1O6cdYVyrZdmmz96yickCGy8uKJggcUwF6A%3D=0>
>  truth I meant universal or divine truth. We can certainly ask everyone for 
> the complete truth as they perceive it - opinion, the first kind of knowledge 
> according to the Dutch 
> philosopher<https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fethicadb.org%2F241=01%7C01%7Cscott.speakman%40panalytical.com%7C04af11f1491744c1a66108d607916d9c%7C071061f3d56946889edeb63a6a7f1ecc%7C0=COtsh1XB996FO0fAwgpPhBf0eWk81zJv149LUucVVJU%3D=0>,
>  and "the only source of falsity" :-) Scientists try to approach the second 
> kind of knowledge (reason). The third kind is divine truth, and even Armel 
> cannot ask for that.

>
On Tue, 21 Aug 2018 at 17:44, Le Bail Armel 
mailto:le-bail.ar...@orange.fr>> wrote:
>

> Dear Rietvelders,

>

> The last sentence of the van Laar & Schenk paper is  :
>
> "It seems to us justified to replace the name ‘Rietveld method’
> in the future by the working title of the past: ‘profile method,’
> or to honour the inventor by using ‘Loopstra method’."
>
> So, shame on Rietveld for having stolen Loopstra idea and mathematics
> from van Laar. Shame also for having modified a paper from Henk Schenk
> telling early the "true."
>
> Thanks to Bob van Laar for being so obviously modest and not
> considering that his mathematics matter in the method.
>
> Hope that among the 700 readers there are a few like me finding
> that paper completely incoherent and not convincing at all.
>
> The fact is that Hugo Rietveld was convinced that he was the
> main conceiver of the method and it is absolutely not impossible
> that Loopstra was only one of the numerous guys who had the idea
> tor fit a complete powder pattern instead of extracted intensities.
> Rietveld himself could be one of such guys. He decided to thank

> Loopstra and van Laar "for their suggestions and helpful criticisms".

> And this supposes that Loopsta and van Laar have very probably

> read the pa

Re: Rietveld

[Le Bail Armel]

The >1500 subscribers can vote... :

 

https://doodle.com/poll/gh3v3nfhue599w23

 

Best,

 

Armel

 

 

 

> Message du 21/08/18 19:10
> De : "Alan Hewat" 
> A : "rietveld_l@ill.fr" 
> Copie à : 
> Objet : Re: Rietveld
> 
>
> As a matter of course we didn't took part in the discussion... (Schenk)
> ...people pretending now to speak in place of Loopstra should stop to do so 
> (Le Bail)
What a contrast of style and substance. Late believers are true believers, and 
Passion evicts Doubt.
>

> 
Seeking sanity, I refer back to Miguel and the meaning of truth and knowledge.:
>
> Scientists cannot ask anyone for the absolute truth  (A consideration valid 
>for one but also for two) 
> By absolute truth I meant universal or divine truth. We can certainly ask 
> everyone for the complete truth as they perceive it - opinion, the first kind 
> of knowledge according to the Dutch philosopher, and "the only source of 
> falsity" :-) Scientists try to approach the second kind of knowledge 
> (reason). The third kind is divine truth, and even Armel cannot ask for that.


>

On Tue, 21 Aug 2018 at 17:44, Le Bail Armel  wrote:
>

> Dear Rietvelders,

>  

> The last sentence of the van Laar & Schenk paper is  :
> 
> "It seems to us justified to replace the name ‘Rietveld method’ 
> in the future by the working title of the past: ‘profile method,’ 
> or to honour the inventor by using ‘Loopstra method’."
> 
> So, shame on Rietveld for having stolen Loopstra idea and mathematics
> from van Laar. Shame also for having modified a paper from Henk Schenk
> telling early the "true."
> 
> Thanks to Bob van Laar for being so obviously modest and not 
> considering that his mathematics matter in the method.
> 
> Hope that among the 700 readers there are a few like me finding
> that paper completely incoherent and not convincing at all.
> 
> The fact is that Hugo Rietveld was convinced that he was the
> main conceiver of the method and it is absolutely not impossible
> that Loopstra was only one of the numerous guys who had the idea
> tor fit a complete powder pattern instead of extracted intensities.
> Rietveld himself could be one of such guys. He decided to thank

> Loopstra and van Laar "for their suggestions and helpful criticisms".

> And this supposes that Loopsta and van Laar have very probably

> read the paper before submission and seen clearly that Rietveld

> was the only author of that now most cited 1969 paper...
> 
> One of the main surprising sentence in the paper is :
> "If the community had awarded this (Loopstra & Rietveld, 1969) 
> paper the recognition it deserved, the described profile refinement 
> method would probably not be named after Rietveld alone. From the 
> point of view of historical correctness this would have been much 
> closer to the truth."
> 
> Indeed, in that 1969 paper one can find :
> "In neutron powder diffraction, it is customary to use as 
> least-squares data the integrated values of the diffraction peaks, 
> even when these consist of more than one Bragg reflexion. The loss 
> of information inherent in this technique can, however, be eliminated 
> by using the complete observed powder pattern in a direct manner 
> (Rietveld, 1967). This method determines the esti-mates of the 
> structure parameters by finding a least-squares fit between the 
> observed and calculated profile intensities."
> 
> So, Loopstra cosigns a paper in 1969 with Rietveld in which he
> recognizes using the Rietveld method as described in the Rietveld
> 1967 paper !
> 
> Later Loopstra published many papers referencing the Rietveld 
> 1969 paper.
> 
> My conclusion is that people pretending now to speak in place
> of Loopstra should stop to do so.
> 
> Best,
> 
> Armel Le Bail
> 
> 
>

> Message du 21/08/18 16:01
> > De : h.sch...@uva.nl
> > A : Rietveld_l@ill.fr
> > Copie à : 
> > Objet : [SUSPECTED SPAM] Rietveld
> > 
> >We were worried that our article was not reaching the powder 
> >crystallographers as it was published, although Open Access, in Acta Cryst 
> >A. Jim Kaduk advised me to use this excellent list-server, so I became 
> >member and posted our message. Now I�m happy to mention that since that day 
> >Acta A counted almost 700 downloads for the paper, so we clearly reached our 
> >goal.
> > 
> > I was also pleased to follow the discussion, very lively and interesting, 
> > and thank all contributors. The discussion was led day and night by our 
> > excellent chair/moderator, Alan Hewat. 
> > Alan, you did a fantastic job, summarising, ad

Re: Rietveld

[Alan Hewat]

*> As a matter of course we didn't took part in the discussi**on... *
(Schenk)
*> ...**people pretending now to speak in place **of Loopstra should stop
to do so *(Le Bail)
What a contrast of style and substance. Late believers are true believers,
and Passion evicts Doubt.

Seeking sanity, I refer back to Miguel and the meaning of truth and
knowledge.:
> *Scientists cannot ask anyone for the absolute truth*  (A consideration
valid for one but also for two)
By absolute  truth I meant
universal or divine truth. We can certainly ask everyone for the complete
truth as they perceive it - opinion, the first kind of knowledge according
to the Dutch philosopher , and "the only source of
falsity" :-) Scientists try to approach the second kind of knowledge
(reason). The third kind is divine truth, and even Armel cannot ask for
that.

On Tue, 21 Aug 2018 at 17:44, Le Bail Armel  wrote:

> Dear Rietvelders,
>
>
>
> The last sentence of the van Laar & Schenk paper is  :
>
> "It seems to us justified to replace the name ‘Rietveld method’
> in the future by the working title of the past: ‘profile method,’
> or to honour the inventor by using ‘Loopstra method’."
>
> So, shame on Rietveld for having stolen Loopstra idea and mathematics
> from van Laar. Shame also for having modified a paper from Henk Schenk
> telling early the "true."
>
> Thanks to Bob van Laar for being so obviously modest and not
> considering that his mathematics matter in the method.
>
> Hope that among the 700 readers there are a few like me finding
> that paper completely incoherent and not convincing at all.
>
> The fact is that Hugo Rietveld was convinced that he was the
> main conceiver of the method and it is absolutely not impossible
> that Loopstra was only one of the numerous guys who had the idea
> tor fit a complete powder pattern instead of extracted intensities.
> Rietveld himself could be one of such guys. He decided to thank
>
> Loopstra and van Laar "for their suggestions and helpful criticisms".
>
> And this supposes that Loopsta and van Laar have very probably
>
> read the paper before submission and seen clearly that Rietveld
>
> was the only author of that now most cited 1969 paper...
>
> One of the main surprising sentence in the paper is :
> "If the community had awarded this (Loopstra & Rietveld, 1969)
> paper the recognition it deserved, the described profile refinement
> method would probably not be named after Rietveld alone. From the
> point of view of historical correctness this would have been much
> closer to the truth."
>
> Indeed, in that 1969 paper one can find :
> "In neutron powder diffraction, it is customary to use as
> least-squares data the integrated values of the diffraction peaks,
> even when these consist of more than one Bragg reflexion. The loss
> of information inherent in this technique can, however, be eliminated
> by using the complete observed powder pattern in a direct manner
> (Rietveld, 1967). This method determines the esti-mates of the
> structure parameters by finding a least-squares fit between the
> observed and calculated profile intensities."
>
> So, Loopstra cosigns a paper in 1969 with Rietveld in which he
> recognizes using the Rietveld method as described in the Rietveld
> 1967 paper !
>
> Later Loopstra published many papers referencing the Rietveld
> 1969 paper.
>
> My conclusion is that people pretending now to speak in place
> of Loopstra should stop to do so.
>
> Best,
>
> Armel Le Bail
>
>
> > Message du 21/08/18 16:01
> > De : h.sch...@uva.nl
> > A : Rietveld_l@ill.fr
> > Copie à :
> > Objet : [SUSPECTED SPAM] Rietveld
> >
> >We were worried that our article was not reaching the powder
> crystallographers as it was published, although Open Access, in Acta Cryst
> A. Jim Kaduk advised me to use this excellent list-server, so I became
> member and posted our message. Now I�m happy to mention that since that day
> Acta A counted almost 700 downloads for the paper, so we clearly reached
> our goal.
> >
> > I was also pleased to follow the discussion, very lively and
> interesting, and thank all contributors. The discussion was led day and
> night by our excellent chair/moderator, Alan Hewat.
> > Alan, you did a fantastic job, summarising, adding information and
> making essential links. Thank you very very much!
> >
> > As a matter of course we didn�t took part in the discussion, but now I
> like to make one comment on the question �why now�. This is a quite long
> story and carries a lot of non-scientific information. So it couldn�t be
> part of our paper, but may be once it will be written down and published in
> the IUCr Newsletter.
> >
> > Henk Schenk
>
>
> ++
> Please do NOT attach files to the whole list  >
> Send commands to  eg: HELP as the subject with no body
> text
> The Rietveld_L list archive is on
> http://www.mail-archive.com/rietveld_l@ill.fr/
> 

Re: Rietveld

[Le Bail Armel]

Dear Rietvelders,

 

The last sentence of the van Laar & Schenk paper is  :

"It seems to us justified to replace the name ‘Rietveld method’ 
in the future by the working title of the past: ‘profile method,’ 
or to honour the inventor by using ‘Loopstra method’."

So, shame on Rietveld for having stolen Loopstra idea and mathematics
from van Laar. Shame also for having modified a paper from Henk Schenk
telling early the "true."

Thanks to Bob van Laar for being so obviously modest and not 
considering that his mathematics matter in the method.

Hope that among the 700 readers there are a few like me finding
that paper completely incoherent and not convincing at all.

The fact is that Hugo Rietveld was convinced that he was the
main conceiver of the method and it is absolutely not impossible
that Loopstra was only one of the numerous guys who had the idea
tor fit a complete powder pattern instead of extracted intensities.
Rietveld himself could be one of such guys. He decided to thank

Loopstra and van Laar "for their suggestions and helpful criticisms".

And this supposes that Loopsta and van Laar have very probably

read the paper before submission and seen clearly that Rietveld

was the only author of that now most cited 1969 paper...

One of the main surprising sentence in the paper is :
"If the community had awarded this (Loopstra & Rietveld, 1969) 
paper the recognition it deserved, the described profile refinement 
method would probably not be named after Rietveld alone. From the 
point of view of historical correctness this would have been much 
closer to the truth."

Indeed, in that 1969 paper one can find :
"In neutron powder diffraction, it is customary to use as 
least-squares data the integrated values of the diffraction peaks, 
even when these consist of more than one Bragg reflexion. The loss 
of information inherent in this technique can, however, be eliminated 
by using the complete observed powder pattern in a direct manner 
(Rietveld, 1967). This method determines the esti-mates of the 
structure parameters by finding a least-squares fit between the 
observed and calculated profile intensities."

So, Loopstra cosigns a paper in 1969 with Rietveld in which he
recognizes using the Rietveld method as described in the Rietveld
1967 paper !

Later Loopstra published many papers referencing the Rietveld 
1969 paper.

My conclusion is that people pretending now to speak in place
of Loopstra should stop to do so.

Best,

Armel Le Bail




> Message du 21/08/18 16:01
> De : h.sch...@uva.nl
> A : Rietveld_l@ill.fr
> Copie à : 
> Objet : [SUSPECTED SPAM] Rietveld
> 
>We were worried that our article was not reaching the powder crystallographers 
>as it was published, although Open Access, in Acta Cryst A. Jim Kaduk advised 
>me to use this excellent list-server, so I became member and posted our 
>message. Now I�m happy to mention that since that day Acta A counted almost 
>700 downloads for the paper, so we clearly reached our goal.
> 
> I was also pleased to follow the discussion, very lively and interesting, and 
> thank all contributors. The discussion was led day and night by our excellent 
> chair/moderator, Alan Hewat. 
> Alan, you did a fantastic job, summarising, adding information and making 
> essential links. Thank you very very much!
> 
> As a matter of course we didn�t took part in the discussion, but now I like 
> to make one comment on the question �why now�. This is a quite long story and 
> carries a lot of non-scientific information. So it couldn�t be part of our 
> paper, but may be once it will be written down and published in the IUCr 
> Newsletter.
> 
> Henk Schenk


++
Please do NOT attach files to the whole list 
Send commands to 
eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++


++
Please do NOT attach files to the whole list 
Send commands to  eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++

Re: Rietveld

[Miguel Delgado]

*/> Loopstra is not alive either/* (A fact. True).

> */Scientists cannot ask anyone for the absolute truth/* (A 
consideration valid for one but also for two, and beyond).


> */We have to look at the available evidence, and different people may 
reach different conclusions./* (A well-based scientific -human- statement)


>*/If you want the opinion of the actual people involved, you now have 
van Laar's account and you have Rietveld's account/*. Again, too bad 
that Dr. Rietveld is not alive. In my humble opinion, for the sake of 
the proper scientific exchange of ideas and facts in the _actual 
context_, Dr. Rietveld’s statements of many years ago is not enough. The 
vL publication, after the passing of Dr. Rietveld, needs a lot more 
than that.



On 8/20/2018 1:47 AM, Alan Hewat wrote:
*> For the sake of the scientific exchange of ideas and facts, too bad 
that Dr. Rietveld is not alive.*
Loopstra is not alive either. Scientists cannot ask anyone for the 
absolute truth. We have to look at the available evidence, and 
different people may reach different conclusions. If you want the 
opinion of the actual people involved, you now have van Laar's account 
<http://journals.iucr.org/a/issues/2018/02/00/ib5058/>  and you have 
Rietveld's account <%20http://home.wxs.nl/%7Erietv025/>.


*> ...why did this happen 49 years after?*
1) At Petten there was apparently a problem from the beginning. 
According to vL <http://journals.iucr.org/a/issues/2018/02/00/ib5058/>
"/After publishing this important project alone, Rietveld found his 
position in the small Petten group increasingly difficult. In 1974 he 
successfully applied for the post of head of the RCN library/"

2) For the first 20 years, it simply wasn't important
"/It was only really adopted by the wider crystallographic community 
20 years later, after the original small group at Petten had all left 
science/".
3) When the importance of the method was finally recognised, these 
reservations about its origins were published, at least in the NL - D. 
Andriesse (2000), H. Schenk (2001) as quoted by vL 
<http://journals.iucr.org/a/issues/2018/02/00/ib5058/>.


*Just as profile refinement "/did not suddenly appear in a flash of 
inspiration of a single person/", questions about the origin of the 
method did not suddenly appear in 2018.*


On Mon, 20 Aug 2018 at 07:35, Davide Levy <mailto:davide.lev...@gmail.com>> wrote:


Hi,

I am too young and out of the mainstream of powder diffraction to
know all the stories about the born of the Rietveld Method.

My question is: the article of Rietveld is published in 1969 and
 the article about the born of this method come out after that
Hugo Rietveld pass away, why did this happen 49 years after?

*Dr. Davide Levy, Ph.D.*

*Head of XRD laboratory
Wolfson Applied Materials Research Center*
*Tel Aviv University*

*Phone: +972-3-6407815 *
*Fax: +972-3-6407819 *
*http://www3.tau.ac.il/wamrc/ <http://www3.tau.ac.il/wamrc/>*


http://www3.tau.ac.il/wamrc/templates/labs_3/images/new-tau-logo.pngWAMRC-LOGO_new

*From:*rietveld_l-requ...@ill.fr
<mailto:rietveld_l-requ...@ill.fr>
[mailto:rietveld_l-requ...@ill.fr
<mailto:rietveld_l-requ...@ill.fr>] *On Behalf Of *Le Bail Armel
*Sent:* Monday, 20 August, 2018 2:22 AM
*To:* Rietveld_l@ill.fr <mailto:Rietveld_l@ill.fr>
*Subject:* Re: Rietveld

*>"...*/*the method did not suddenly appear in a flash of
inspiration of a single person, but was the result of the work of
three individuals... Loopstra, van Laar and Rietveld.*/*".*

And more precisely :

" HS wrote in Dutch:

‘Loopstra had the idea that it should be better to use the whole
powder profile rather than estimated intensities to solve
structures, van Laar worked it out mathematically and Rietveld
programmed it."

I conclude then :

no idea for Rietveld and van Laar since they are from Loopstra;

no mathematics for Rietveld and Loopstra;

no programming for Loopstra and van Laar.

A very clear result of the work of three individuals. The HS view...

Seems that Rietveld had not the same opinion and claimed for ideas
too and possibly for mathematics as well.

Best,

Armel

++
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Send commands to mailto:lists...@ill.fr>> eg:
HELP as the subject with no body text
The Rietveld_L list archive is on
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++



--
__
*   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__


+

Re: Rietveld

[Alan Hewat]

*>  For the sake of the scientific exchange of ideas and facts, too bad
that Dr. Rietveld is not alive.*
Loopstra is not alive either. Scientists cannot ask anyone for the absolute
truth. We have to look at the available evidence, and different people may
reach different conclusions. If you want the opinion of the actual people
involved, you now have van Laar's account
<http://journals.iucr.org/a/issues/2018/02/00/ib5058/>  and you have Rietveld's
account <http://home.wxs.nl/~rietv025/>.

*> ...why did this happen 49 years after?*
1) At Petten there was apparently a problem from the beginning. According
to vL <http://journals.iucr.org/a/issues/2018/02/00/ib5058/>
"*After publishing this important project alone, Rietveld found his
position in the small Petten group increasingly difficult. In 1974 he
successfully applied for the post of head of the RCN library*"
2) For the first 20 years, it simply wasn't important
"*It was only really adopted by the wider crystallographic community 20
years later, after the original small group at Petten had all left science*
".
3) When the importance of the method was finally recognised, these
reservations about its origins were published, at least in the NL - D.
Andriesse (2000), H. Schenk (2001) as quoted by vL
<http://journals.iucr.org/a/issues/2018/02/00/ib5058/>.

*Just as profile refinement "did not suddenly appear in a flash of
inspiration of a single person", questions about the origin of the method
did not suddenly appear in 2018.*

On Mon, 20 Aug 2018 at 07:35, Davide Levy  wrote:

> Hi,
>
> I am too young and out of the mainstream of powder diffraction to know all
> the stories about the born of the Rietveld Method.
>
> My question is: the article of Rietveld is published in 1969 and  the
> article about the born of this method come out after that Hugo Rietveld
> pass away, why did this happen 49 years after?
>
>
>
> *Dr. Davide Levy, Ph.D.*
>
>
> *Head of XRD laboratoryWolfson Applied Materials Research Center*
> *Tel Aviv University*
>
> *Phone: +972-3-6407815 <+972%203-640-7815>*
> *Fax:   +972-3-6407819 <+972%203-640-7819>*
> *http://www3.tau.ac.il/wamrc/  <http://www3.tau.ac.il/wamrc/>*
>
> [image:
> http://www3.tau.ac.il/wamrc/templates/labs_3/images/new-tau-logo.png][image:
> WAMRC-LOGO_new]
>
>
>
> *From:* rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] *On
> Behalf Of *Le Bail Armel
> *Sent:* Monday, 20 August, 2018 2:22 AM
> *To:* Rietveld_l@ill.fr
> *Subject:* Re: Rietveld
>
>
>
>
>
> *>"...**the method did not suddenly appear in a flash of inspiration of a
> single person, but was the result of the work of three individuals...
> Loopstra, van Laar and Rietveld.**".*
>
>
>
> And more precisely :
>
>
>
> " HS wrote in Dutch:
>
> ‘Loopstra had the idea that it should be better to use the whole powder
> profile rather than estimated intensities to solve structures, van Laar
> worked it out mathematically and Rietveld programmed it."
>
>
>
> I conclude then :
>
> no idea for Rietveld and van Laar since they are from Loopstra;
>
> no mathematics for Rietveld and Loopstra;
>
> no programming for Loopstra and van Laar.
>
>
>
> A very clear result of the work of three individuals. The HS view...
>
>
>
> Seems that Rietveld had not the same opinion and claimed for ideas too and
> possibly for mathematics as well.
>
>
>
> Best,
>
>
>
> Armel
>
>
>
>
>
>
> ++
> Please do NOT attach files to the whole list  >
> Send commands to  eg: HELP as the subject with no body
> text
> The Rietveld_L list archive is on
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++
>
>

-- 
__
*   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
++
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++

RE: Rietveld

[Davide Levy]

Hi,

I am too young and out of the mainstream of powder diffraction to know all the 
stories about the born of the Rietveld Method. 

My question is: the article of Rietveld is published in 1969 and  the article 
about the born of this method come out after that Hugo Rietveld pass away, why 
did this happen 49 years after? 

 

Dr. Davide Levy, Ph.D.

Head of XRD laboratory
Wolfson Applied Materials Research Center
Tel Aviv University

Phone:   +972-3-6407815
Fax: +972-3-6407819
 <http://www3.tau.ac.il/wamrc/ > http://www3.tau.ac.il/wamrc/ 



 

From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On Behalf Of 
Le Bail Armel
Sent: Monday, 20 August, 2018 2:22 AM
To: Rietveld_l@ill.fr
Subject: Re: Rietveld

 

 

>"...the method did not suddenly appear in a flash of inspiration of a single 
>person, but was the result of the work of three individuals... Loopstra, van 
>Laar and Rietveld.".

 

And more precisely :

 

" HS wrote in Dutch:

‘Loopstra had the idea that it should be better to use the whole powder profile 
rather than estimated intensities to solve structures, van Laar worked it out 
mathematically and Rietveld programmed it."

 

I conclude then :

no idea for Rietveld and van Laar since they are from Loopstra;

no mathematics for Rietveld and Loopstra;

no programming for Loopstra and van Laar.

 

A very clear result of the work of three individuals. The HS view...

 

Seems that Rietveld had not the same opinion and claimed for ideas too and 
possibly for mathematics as well.

 

Best,

 

Armel

 

 

 

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++

Re: Rietveld

[Miguel Delgado]

Seems that Rietveld had not the same opinion and claimed for ideas too 
and possibly for mathematics as well.


Best,

Armel



Armel,

For the sake of the scientific exchange of ideas and facts, too bad that 
Dr. Rietveld is not alive.


Regards,

Miguel Delgado


On 8/19/2018 6:21 PM, Le Bail Armel wrote:


*>".../the method did not suddenly appear in a flash of inspiration of 
a single person, but was the result of the work of three 
individuals... Loopstra, van Laar and Rietveld./".*


And more precisely :

" HS wrote in Dutch:

‘Loopstra had the idea that it should be better to use the whole 
powder profile rather than estimated intensities to solve structures, 
van Laar worked it out mathematically and Rietveld programmed it."


I conclude then :

no idea for Rietveld and van Laar since they are from Loopstra;

no mathematics for Rietveld and Loopstra;

no programming for Loopstra and van Laar.

A very clear result of the work of three individuals. The HS view...

Seems that Rietveld had not the same opinion and claimed for ideas too 
and possibly for mathematics as well.


Best,

Armel



++
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++



++
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++

Re: Rietveld

[Le Bail Armel]

 

>"...the method did not suddenly appear in a flash of inspiration of a single 
>person, but was the result of the work of three individuals... Loopstra, van 
>Laar and Rietveld.".

 

And more precisely :

 

" HS wrote in Dutch:

‘Loopstra had the idea that it should be better to use the whole powder profile 
rather than estimated intensities to solve structures, van Laar worked it out 
mathematically and Rietveld programmed it."

 

I conclude then :

no idea for Rietveld and van Laar since they are from Loopstra;

no mathematics for Rietveld and Loopstra;

no programming for Loopstra and van Laar.

 

A very clear result of the work of three individuals. The HS view...

 

Seems that Rietveld had not the same opinion and claimed for ideas too and 
possibly for mathematics as well.

 

Best,

 

Armel

 

 

 
++
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++

Re: Rietveld

[Alan Hewat]

>  Seriously, HS really think that Hugo Rietveld had absolutely no idea,
and then worked out mathematically nothing ?

Armel, the vL paper
 doesn't
say that Rietveld had no idea and contributed nothing. Please read the
first line of the paper again.

*"...the method did not suddenly appear in a flash of inspiration of a
single person, but was the result of the work of three individuals...
Loopstra, van Laar and Rietveld.".*

But it's great to see you back on the Rietveld mailing list, pushing hard
for what you Believe :-)  Alan.
__
*   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
++
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++

Re: Rietveld

[Le Bail Armel]

Hi,

 

Reading again the Acta Cryst. (2018). A74, 88–92 paper :

 

"So, summarized here, HS wrote in Dutch:

‘Loopstra had the idea that it should be better to use the whole powder profile 
rather than estimated intensities to solve structures, van Laar worked it out 
mathematically and Rietveld programmed it. Nowadays it is known as the Rietveld 
method’. HS submitted the raw manuscript without figures and photographs. At the 
time he was President of the IUCr, very busy and travelling a lot. So when he 
saw the article again, it was already printed, there were four illustrations 
provided by Rietveld himself, and slight changes had been made to the text, 
which in essence had changed its meaning. In the sentence above Loopstra was 
replaced by Rietveld and it now started with ‘Rietveld had the idea that...’. 
Also a last sentence about Rietveld’s hobby, as a jazz pianist, had been added."

 

This is the "coup de grace"...

 

But could Hugo Rietveld admit to be transformed in a simple programmer by  
‘Loopstra had the idea that it should be better to use the whole powder profile 
rather than estimated intensities to solve structures, van Laar worked it out 
mathematically and Rietveld programmed it' ?

 

Seriously, HS really think that Hugo Rietveld had absolutely no idea, and then 
worked out mathematically nothing ?

 

This was a complete provocation to give to Hugo Rietveld access to such an 
insulting text against him before its publication.

 

I just prefer to believe that Hugo Rietveld restored the truth by inserting 
‘Rietveld had the idea that...’. instead of Loopstra.

 

There is no proof of the contrary given by Loopstra himself, defined as a man 
"who apparently pushed hard" by Alan. He had a lot of time to push hard in 
order to contradict the legend and has done nothing apart using the method and 
citing quietly the 1969 paper from Hugo Rietveld.

 

Best,

 

Armel

 

 

 

 

 

 

> Message du 18/08/18 12:24
> De : "Alan Hewat" 
> A : le-bail.ar...@orange.fr
> Copie à : "rietveld_l@ill.fr" 
> Objet : Re: Rietveld
> 
>
> As I get older, I believe less and less in legends  (AH)
> 
> ...the aristocracy of powder diffractionists is displaced (AleB)

>
I don't believe in aristocracy either :-) After Bill David, Lambert van Eijck 
and I published Hugo Rietveld's glowing obituary, I received a rough draft of 
the vL paper, and was frankly shocked. But after finding that others shared 
those views, I suggested a re-write of the paper to make it (perhaps) less 
controversial and more historical, supported where possible with evidence from 
the literature. Still, the paper seemed to address questions I myself had about 
the legend.

>
1) How could a young man, educated as a classical crystallographer (Bragg 
peaks, structure factors, Fourier transforms...) produce the revolutionary idea 
of simply refining the structure to fit the observed profile ? None of the 
professional crystallographers I knew accepted that idea - only physicists and 
chemists who used crystallography as a tool. It was a naive physicist's 
approach.

>
2) How could Rietveld (1967) in his first paper not emphasise this 
revolutionary departure from classical crystallographic techniques ? It was 
almost as if he didn't consider that refining  magnetic moments and atom 
displacements was real crystallography, just a refinement problem where 
compromises had to be made to get a required result with an inadequate computer.

>
3) Why did Rietveld leave science in 1974 if he thought that he had achieved 
something remarkable ? He had a permanent job at a well funded laboratory and a 
technique that would eventually revolutionise powder diffraction. Ordinary 
people like me couldn't even get a job at Cambridge (thanks Mike :-) and had to 
live with a succession of 3 year contracts in foreign countries.

>
When I first knew Hugo, he was a modest, unassuming man, unlike Loopstra who 
apparently pushed hard. When he saw that "The response was slight, or, rather, 
non-existent" perhaps like other crystallographers for 20 years he himself 
doubted the value of profile refinement.

>
And no I don't think the crystallographic establishment should get to name it. 
Everyone knows what "profile refinement" means.


>

On Sat, 18 Aug 2018 at 11:29, Le Bail Armel  wrote:
>

> Hi,

>  

> >As I get older, I believe less and less in legends. In the IUCr 1999 issue 
> >that I cited, I should have also mentioned that there is an interesting 
> >article on p.4 called "The Powder Diffraction Handicap" by Armel le Bail :-)

>  

> Indeed, "never say never" is verified again. The powder diffraction handicap 
> (overlapping) can be considered as suppressed by XFEL

> https://www.xfel.eu/ where each single microcrystal of the powder produces 3D 
> diffraction dat

Re: Rietveld

[Alan Hewat]

*> As I get older, I believe less and less in legends  (AH)*
*> ...the aristocracy of powder diffractionists is displaced (AleB)*

I don't believe in aristocracy either :-) After Bill David, Lambert van
Eijck and I published Hugo Rietveld's glowing obituary
, I received a rough
draft of the vL paper
, and was frankly
shocked. But after finding that others shared those views, I suggested a
re-write of the paper to make it (perhaps) less controversial and more
historical, supported where possible with evidence from the literature.
Still, the paper seemed to address questions I myself had about the legend.

1) How could a young man, educated as a classical crystallographer (Bragg
peaks, structure factors, Fourier transforms...) produce the revolutionary
idea of simply refining the structure to fit the observed profile ? None of
the professional crystallographers I knew accepted that idea - only
physicists and chemists who used crystallography as a tool. It was a naive
physicist's approach.

2) How could Rietveld (1967) in his first paper not emphasise this
revolutionary departure from classical crystallographic techniques ? It was
almost as if he didn't consider that refining  magnetic moments and atom
displacements was real crystallography, just a refinement problem where
compromises had to be made to get a required result with an inadequate
computer.

3) Why did Rietveld leave science in 1974 if he thought that he had
achieved something remarkable ? He had a permanent job at a well funded
laboratory and a technique that would eventually revolutionise powder
diffraction. Ordinary people like me couldn't even get a job at Cambridge
(thanks Mike :-) and had to live with a succession of 3 year contracts in
foreign countries.

When I first knew Hugo, he was a modest, unassuming man, unlike Loopstra
who apparently pushed hard. When he saw that "*The response was slight, or,
rather, non-existent*" perhaps like other crystallographers for 20 years he
himself doubted the value of profile refinement.

And no I don't think the crystallographic establishment should get to name
it. Everyone knows what "profile refinement" means.

On Sat, 18 Aug 2018 at 11:29, Le Bail Armel  wrote:

> Hi,
>
>
>
> >As I get older, I believe less and less in legends. In the IUCr 1999
> issue that I cited, I should have also mentioned that there is an
> interesting article on p.4 called "*The Powder Diffraction Handicap
> *" by Armel le Bail :-)
>
>
>
> Indeed, "never say never" is verified again. The powder diffraction
> handicap (overlapping) can be considered as suppressed by XFEL
>
> https://www.xfel.eu/ where each single microcrystal of the powder
> produces 3D diffraction data, and all data are recombined !
>
> But for solving too simple problems, you will not have access to that
> overloaded machine and will have to continue to use your laboratory powder
> diffractometer and (now) classical approaches.
>
>
>
> So, once again, the aristocracy of powder diffractionists is displaced,
> this time from third generation synchrotron to XFEL, amusing, new legends
> will be built, probably.
>
>
>
> Best,
>
>
>
> Armel
>
>
> ++
> Please do NOT attach files to the whole list  >
> Send commands to  eg: HELP as the subject with no body
> text
> The Rietveld_L list archive is on
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++
>
>

-- 
__
*   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
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++

Re: Rietveld

[Le Bail Armel]

Hi,

 

>As I get older, I believe less and less in legends. In the IUCr 1999 issue 
>that I cited, I should have also mentioned that there is an interesting 
>article on p.4 called "The Powder Diffraction Handicap" by Armel le Bail :-)

 

Indeed, "never say never" is verified again. The powder diffraction handicap 
(overlapping) can be considered as suppressed by XFEL

https://www.xfel.eu/ where each single microcrystal of the powder produces 3D 
diffraction data, and all data are recombined !

But for solving too simple problems, you will not have access to that 
overloaded machine and will have to continue to use your laboratory powder 
diffractometer and (now) classical approaches. 

 

So, once again, the aristocracy of powder diffractionists is displaced, this 
time from third generation synchrotron to XFEL, amusing, new legends will be 
built, probably.

 

Best,

 

Armel

 
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++

Re: Rietveld

[David Elbert]

I am an interested reader of this thread, but have no direct knowledge of any 
of the history.  I will add, however, a small point about Alan’s last note 
suggesting we could go back to calling the process “Profile Refinement” and 
dodge the personal attribution. 

My point is that naming things after people may over simplify attribution, but 
it also does a larger service by emphasizing that science is a process done by 
people.  Science is not, as some uninitiated believe, simply a cold statement 
or revelation of facts.  People *do* science while simultaneously *guiding* or 
even inventing the science.  They define what become interesting problems while 
human curiosity and interests provide the driving force in the direction of 
scientific work. 

Naming things is an important part of how humans think about things and 
associating ideas or techniques with a scientist or group is an accurate way of 
representing how the process of science works. It is a human process and I’d 
rather not expunge that even though the attribution can rarely capture the full 
scope of the history.

That’s my two-cents as we say here in the US.

-David


David Elbert
Hopkins Extreme Materials Institute
Malone Hall
Johns Hopkins University
3400 N. Charles St
Baltimore, MD 21218

(410) 516-5049

elbert_at_jhu.edu






> On Aug 17, 2018, at 5:30 AM, Alan Hewat  wrote:
> 
> >  ...your responsibility in establishing and approving the legend is quite 
> > high
> >  Then times to destroy the legend come, and you want to be a part of it 
> > too, apparently.
> 
> As I get older, I believe less and less in legends. In the IUCr 1999 issue 
> that I cited, I should have also mentioned that there is an interesting 
> article on p.4 called "The Powder Diffraction Handicap 
> " by Armel le Bail :-)
> 
> I personally think we should use Rietveld's original term "Profile 
> Refinement", which I already used in my Harwell report 
> 1973_The_Rietveld_Program_for_the_Profile_Refinement_of_ 
> Neutron_Diffraction_Powder_Patterns_AERE_R7350-von_Dreele_annotations.pdf 
> 
>   
> 
> On Fri, 17 Aug 2018 at 10:31, Le Bail Armel  > wrote:
>  
> >Probably, that's how legends begin.
> 
>  
> Your presence on so many pictures together with Hugo Rietveld, suggests that 
> your responsibility in establishing and approving the legend is quite high, 
> between 30 and 60% maybe, but I recognize that Rwp is poorly satisfying for 
> this fit.
> 
> http://home.wxs.nl/~rietv025/crystallografen-s.jpg 
> 
>  
> Then times to destroy the legend come, and you want to be a part of it too, 
> apparently.
> 
>  
> Should we rename the Rietveld decomposition formula (equation 7 in his 1969 
> paper) the Loopstra decomposition formula ? I am lost.
> 
>  
> Best,
> 
>  
> Armel
> 
> ++
> Please do NOT attach files to the whole list 
> Send commands to mailto:lists...@ill.fr>> eg: HELP as the 
> subject with no body text
> The Rietveld_L list archive is on 
> http://www.mail-archive.com/rietveld_l@ill.fr/ 
> 
> ++
> 
> 
> 
> -- 
> __
>Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE 
>  +33.476.98.41.68
> http://www.NeutronOptics.com/hewat 
> 
> __
> ++
> Please do NOT attach files to the whole list 
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> The Rietveld_L list archive is on 
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++
> 

++
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++

RE: Rietveld

[Radovan Cerny]

« Profile refinement » is misleading as with Rietveld method we are refining 
also the crystal structure …

I think that it is too late to change the terminology in the text books. The 
history of science is full of wrong legends. One point of view of the people 
involved in the story is now published in the article, and as Hugo Rietveld 
cannot answer the questions, there is no sense to correct the terminology. 
Maybe, our respective bodies CPD-IUCr and EPDIComm may give a recommendation?

Radovan Cerny
Laboratoire de Cristallographie, DQMP
Université de Genève
24, quai Ernest-Ansermet
CH-1211 Geneva 4, Switzerland
Phone  : [+[41] 22] 37 964 50, FAX : [+[41] 22] 37 961 08
mailto : radovan.ce...@unige.ch<mailto:radovan.ce...@unige.ch>
URL: http://www.unige.ch/sciences/crystal/cerny/rcerny.htm

De : rietveld_l-requ...@ill.fr  De la part de Alan 
Hewat
Envoyé : vendredi 17 août 2018 11:31
À : rietveld_l@ill.fr
Objet : Re: Rietveld

>  ...your responsibility in establishing and approving the legend is quite high
>  Then times to destroy the legend come, and you want to be a part of it too, 
> apparently.

As I get older, I believe less and less in legends. In the IUCr 1999 issue that 
I cited, I should have also mentioned that there is an interesting article on 
p.4 called "The Powder Diffraction 
Handicap<http://ww1.iucr.org/news/v7n4/7-4.pdf>" by Armel le Bail :-)

I personally think we should use Rietveld's original term "Profile Refinement", 
which I already used in my Harwell report 
1973_The_Rietveld_Program_for_the_Profile_Refinement_of_ 
Neutron_Diffraction_Powder_Patterns_AERE_R7350-von_Dreele_annotations.pdf<http://hewat.net/science/papers/1973_The_Rietveld_Program_for_the_Profile_Refinement_of_%20Neutron_Diffraction_Powder_Patterns_AERE_R7350-von_Dreele_annotations.pdf>

On Fri, 17 Aug 2018 at 10:31, Le Bail Armel 
mailto:le-bail.ar...@orange.fr>> wrote:



>Probably, that's how legends begin.



Your presence on so many pictures together with Hugo Rietveld, suggests that 
your responsibility in establishing and approving the legend is quite high, 
between 30 and 60% maybe, but I recognize that Rwp is poorly satisfying for 
this fit.

http://home.wxs.nl/~rietv025/crystallografen-s.jpg



Then times to destroy the legend come, and you want to be a part of it too, 
apparently.



Should we rename the Rietveld decomposition formula (equation 7 in his 1969 
paper) the Loopstra decomposition formula ? I am lost.



Best,



Armel
++
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mailto:alan.he...@neutronoptics.com>>
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++


--
__
   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE
mailto:alan.he...@neutronoptics.com>> 
+33.476.98.41.68
http://www.NeutronOptics.com/hewat
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Re: Rietveld

[Alan Hewat]

>  ...your responsibility in establishing and approving the legend is quite
high
>  Then times to destroy the legend come, and you want to be a part of it
too, apparently.

As I get older, I believe less and less in legends. In the IUCr 1999 issue
that I cited, I should have also mentioned that there is an interesting
article on p.4 called "*The Powder Diffraction Handicap
*" by Armel le Bail :-)

I personally think we should use Rietveld's original term "Profile
Refinement", which I already used in my Harwell report
1973_The_Rietveld_Program_for_the_Profile_Refinement_of_
Neutron_Diffraction_Powder_Patterns_AERE_R7350-von_Dreele_annotations.pdf



On Fri, 17 Aug 2018 at 10:31, Le Bail Armel  wrote:

>
>
> >Probably, that's how legends begin.
>
>
>
> Your presence on so many pictures together with Hugo Rietveld, suggests
> that your responsibility in establishing and approving the legend is quite
> high, between 30 and 60% maybe, but I recognize that Rwp is poorly
> satisfying for this fit.
>
> http://home.wxs.nl/~rietv025/crystallografen-s.jpg
>
>
>
> Then times to destroy the legend come, and you want to be a part of it
> too, apparently.
>
>
>
> Should we rename the Rietveld decomposition formula (equation 7 in his
> 1969 paper) the Loopstra decomposition formula ? I am lost.
>
>
>
> Best,
>
>
>
> Armel
> ++
> Please do NOT attach files to the whole list  >
> Send commands to  eg: HELP as the subject with no body
> text
> The Rietveld_L list archive is on
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++
>
>

-- 
__
*   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
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++

Re: Rietveld

[Le Bail Armel]

 

>Probably, that's how legends begin.

 

Your presence on so many pictures together with Hugo Rietveld, suggests that 
your responsibility in establishing and approving the legend is quite high, 
between 30 and 60% maybe, but I recognize that Rwp is poorly satisfying for 
this fit.

http://home.wxs.nl/~rietv025/crystallografen-s.jpg

 

Then times to destroy the legend come, and you want to be a part of it too, 
apparently.

 

Should we rename the Rietveld decomposition formula (equation 7 in his 1969 
paper) the Loopstra decomposition formula ? I am lost.

 

Best,

 

Armel
++
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++

Re: Rietveld

[Alan Hewat]

Armel's supervisor, Daniel Louer, made important contributions to the
description of the line shape for profile refinement with x-rays, but that
was 10 years later. His 1986 paper
 references Rietveld (1969) but
uses a different type of profile refinement developed by Sonneveld & Visser
(1975). "*The strategy consists of the refinement of different peaks in a
cluster, one at a time..."*

Daniel was eventually won over to the Petten method, and there is a nice
picture of him with Hugo at the 1999 IUCr Glasgow symposium that I
organised on "30 Years of Rietveld Refinement
" (page 7).

At my age, I prefer Googling the literature rather than relying on my
remembrances :-)

On Fri, 17 Aug 2018 at 00:22, Alan Hewat 
wrote:

> > * I remember that a Fortran version was in tests there (in Rennes in
> 1975-76), probably one of these 27 copies distributed by Hugo Rietveld
> himself to institutes all over the world.*
>
> Rietveld worked with neutron powder diffraction on magnetic and heavy
> metal oxides. An x-ray lab. in Rennes was probably not one of the selected
> 27 institutes all over the world. As Rietveld wrote in the paper you cited,
> "*The response was slight, or, rather, non-existent*", and by 1975-76 he
> had already left science. Probably, that's how legends begin.
>
> On Thu, 16 Aug 2018 at 21:05, Le Bail Armel 
> wrote:
>
>> Hi,
>>
>>
>>
>> Sorry for that blank email...
>>
>> Since times are to old stories about the Rietveld method, I first
>> heard about it in 1975-76 during my "3ème cycle" thesis in D. Grandjean
>> laboratory, Rennes, France, under the direction of D. Louër. The thesis
>> was about profile-shapes broadening due to powder small grain size.
>> http://www.cristal.org/rapport/Le-Bail-These-3eme-Cycle.pdf
>>
>> I did not use the Rietveld method at that time but I remember that
>> a Fortran version was in tests there, probably one of these 27 copies
>> distributed by Hugo Rietveld himself to institutes all over the world.
>> http://home.wxs.nl/~rietv025/Rietveld%20Method.docx
>>
>> My profile shapes were quite Lorentzian and there was considerable
>> anisotropic broadening, something not yet accountable by the Rietveld
>> method at that time focused on Gaussian peak shapes.
>>
>> I was not back about the Rietveld method before the XIII IUCr Congress,
>> 1984, Hamburg, where I proposed a way to undertake such X-ray complex
>> shapes: "The Rietveld method using an experimental profile convoluted
>> by adjustable analytical function". This was the ARIT software later
>> used in 1987 for intensities extraction purposes by iterating the
>> Rietveld decomposition formula, leading to many SDPDs (Structure
>> Determination by Powder Diffractometry).
>> http://cristal.org/mespapiers-PDF/1984/1984-Rietveld-a31186.pdf
>> http://www.cristal.org/arit.html
>>
>> Best,
>>
>>
>>
>> Armel
>>
>>
>>
>> PS- Better to write your own story clearly yourself before to leave the
>> planet,
>>
>> even if nobody apparently read it.
>>
>> http://www.cristal.org/iniref/lbm-story/
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> ++
>> Please do NOT attach files to the whole list > >
>> Send commands to  eg: HELP as the subject with no body
>> text
>> The Rietveld_L list archive is on
>> http://www.mail-archive.com/rietveld_l@ill.fr/
>> ++
>>
>>
>
> --
> __
> *   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
>  +33.476.98.41.68
> http://www.NeutronOptics.com/hewat
> __
>


-- 
__
*   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
++
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++

Re: Rietveld

[Alan Hewat]

> * I remember that a Fortran version was in tests there (in Rennes in
1975-76), probably one of these 27 copies distributed by Hugo Rietveld
himself to institutes all over the world.*

Rietveld worked with neutron powder diffraction on magnetic and heavy metal
oxides. An x-ray lab. in Rennes was probably not one of the selected 27
institutes all over the world. As Rietveld wrote in the paper you cited, "*The
response was slight, or, rather, non-existent*", and by 1975-76 he had
already left science. Probably, that's how legends begin.

On Thu, 16 Aug 2018 at 21:05, Le Bail Armel  wrote:

> Hi,
>
>
>
> Sorry for that blank email...
>
> Since times are to old stories about the Rietveld method, I first
> heard about it in 1975-76 during my "3ème cycle" thesis in D. Grandjean
> laboratory, Rennes, France, under the direction of D. Louër. The thesis
> was about profile-shapes broadening due to powder small grain size.
> http://www.cristal.org/rapport/Le-Bail-These-3eme-Cycle.pdf
>
> I did not use the Rietveld method at that time but I remember that
> a Fortran version was in tests there, probably one of these 27 copies
> distributed by Hugo Rietveld himself to institutes all over the world.
> http://home.wxs.nl/~rietv025/Rietveld%20Method.docx
>
> My profile shapes were quite Lorentzian and there was considerable
> anisotropic broadening, something not yet accountable by the Rietveld
> method at that time focused on Gaussian peak shapes.
>
> I was not back about the Rietveld method before the XIII IUCr Congress,
> 1984, Hamburg, where I proposed a way to undertake such X-ray complex
> shapes: "The Rietveld method using an experimental profile convoluted
> by adjustable analytical function". This was the ARIT software later
> used in 1987 for intensities extraction purposes by iterating the
> Rietveld decomposition formula, leading to many SDPDs (Structure
> Determination by Powder Diffractometry).
> http://cristal.org/mespapiers-PDF/1984/1984-Rietveld-a31186.pdf
> http://www.cristal.org/arit.html
>
> Best,
>
>
>
> Armel
>
>
>
> PS- Better to write your own story clearly yourself before to leave the
> planet,
>
> even if nobody apparently read it.
>
> http://www.cristal.org/iniref/lbm-story/
>
>
>
>
>
>
>
>
>
>
>
>
> ++
> Please do NOT attach files to the whole list  >
> Send commands to  eg: HELP as the subject with no body
> text
> The Rietveld_L list archive is on
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++
>
>

-- 
__
*   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
++
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++

Re: Rietveld list subscription

[Alan Hewat]

>
> That means after identifying impurity phases, we should keep cell
> parameters and and all shape parameters fixed for impurity phases in
> Rietveld refinement and refine only scale factor of these phases along with
> main phase and then refine all cell parameters and and all shape parameters
> for the main phase?
>

Yes. Then you can refine the cell parameters and scale factors for the
impurity phases. Be careful not to include too many peak shape parameters -
start by constraining them to be the same for all phases.
__
*   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE *
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
++
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++

RE: Rietveld refinement in TOPAS with parallel beam geometry

[Cline, James Dr.]

Patrick,


From: Patrick Price [patrickpric...@gmail.com]
Sent: Friday, December 04, 2009 6:30 AM
To: Rietveld_l@ill.fr
Subject: Rietveld refinement in TOPAS with parallel beam geometry

Since this is my first post I will start with a brief introduction. My
name is Patrick Price and I am in my second year of graduate school.
My thesis work involves the investigation of phase equilibria in
perovskites.

I am using a Bruker D8 Discover diffractometer with parallel beam
geometry. The diffractometer has a Cu K-alpha X-Ray source with a Si
Gobel mirror and a Ge monochromator giving a parallel beam
monochromatic x-ray source.

This instrument description doesn't make sense.

Regards,

Jim


 The receiving side has Soller slits and a
Tl-doped NaI point detector. I am trying to teach myself how to use
TOPAS to PROPERLY analyze my data using Rietveld refinement
techniques.

I have recently taken a scan of the NIST line profile 660 LaB6
standard followed by scans of my perovskite powders using a step size
of 0.02 degrees and scan time of 4 seconds.

Most of the articles I have read are specific to convergent/divergent
beam geometries and I do not know how much of that information
transfers to parallel beam geometries. If anyone could help me answer
the following questions I would greatly appreciate it. These questions
mainly address which parameters should be refined with the LaB6
standard when using parallel beam geometry.
1.  I need to use the scan of the LaB6 powders to characterize the
contributions of the instrument to the diffraction profile. Starting
with the emission profile, TOPAS asks for the wavelength, the Area,
and the Lorentz Half Width. First, I assume the wavelength I should be
the more recent Cu Ka wavelength of 0.154059 nm instead of 0.154056
nm. Second, does Cu Ka have a definite Lorentz HW and “Area” or should
these parameters be refined with the LaB6 diffraction pattern?
2.  Since I have a Ge monochromater I assume the Lorentz polarization
factor should be fixed at 27.3 (Is this correct?). Obviously the
lattice parameters and atomic positions would be fixed.
3.   I read that you should NOT refine both the zero shift error and
sample displacement, and since it is parallel beam I only refine the
zero shift error. Should I refine surface roughness, absorption, or
sample tilt with the LaB6? (Currently I do not refine these)
4.  Am I correct in assuming that I do not have any EQUITORIAL
convolutions (e.g. from slits, FDS, beam spill, VDS) since it is
parallel beam geometry? What about TUBE TAILS?
5.  I am using the Finger_et_al  method to refine the AXIAL
convolutions, however I often get a large error associated with the S
value (sample length), even when my GOF is decent (1.45). Do any of
you know why this would happen?
6.  Should I refine the “Scale” or scale factor. (Currently I do)
7.  IMPORTANT: Originally I was refining the crystallite size but it
always refined to a very small value (~300nm), where as NIST claims
660 LAB6 should have a mean grain size of a few microns or more. I
assume this happens because the TOPAS is accounting for instrument
caused peak broadening by making the crystallite size smaller than it
actually is in the software. However, when I do refine the grain size
I do get a better fit. Should I leave this unchecked, refine it, or
fix it at a reasonable value of ~2500 nm.

In summary, currently I am only refining the Lorentz HW and “Area” in
the emission profile, zero shift error, the Finger parameters (S  H),
the scale factor, and nothing else.
I am unsure if I should be refining anything else such as the
crystallite size, tube tails and other forms of equatorial
convergence, or if there is something else that is important which I
am disregarding completely. I am also unsure if I am correct in
refining Lorentz HW and area in the emission profile.
Sorry if I got a little long winded; I just wanted to give enough
detail so people could answer. Thank you in advance for your help.
Patrick




James P. Cline
Ceramics Division   
National Institute of Standards and Technology
100 Bureau Dr. stop 8520 [ B113 / Bldg 217 ]
Gaithersburg, MD 20899-8523USA
jcl...@nist.gov
(301) 975 5793
FAX (301) 975 5334

Re: Rietveld refinement in TOPAS with parallel beam geometry

[Patrick Price]

Sorry about the confusion on the instrument configuration. I am new to
the field of x-ray diffraction. Hopefully this helps.
The Bruker D8 uses reflection geometry and a THETA : THETA goniometer,
where the x-ray source and detector can be move simultaneously on the
arms of the goniometer.  The x-ray source is Cu and is directed at a
Bruker multipurpose Si Gobel mirror which reflects a parallel beam of
Cu K-alpha (12) radiation at a 2-bounce Ge(022) analyzer crystal.  As
I understand it, the analyzer crystal filters our the K-alpha 2 peak,
producing monochromatic K-alpha 1radiation. There are no soller slits
on the primary side of the instrument. The beam is directed at the
specimen and the diffracted beam passes through a set of soller slits
and then to the point detector.
Thanks,
Patrick

On Fri, Dec 4, 2009 at 5:59 AM, Cline, James Dr. james.cl...@nist.gov wrote:
 Patrick,

 
 From: Patrick Price [patrickpric...@gmail.com]
 Sent: Friday, December 04, 2009 6:30 AM
 To: Rietveld_l@ill.fr
 Subject: Rietveld refinement in TOPAS with parallel beam geometry

 Since this is my first post I will start with a brief introduction. My
 name is Patrick Price and I am in my second year of graduate school.
 My thesis work involves the investigation of phase equilibria in
 perovskites.

 I am using a Bruker D8 Discover diffractometer with parallel beam
 geometry. The diffractometer has a Cu K-alpha X-Ray source with a Si
 Gobel mirror and a Ge monochromator giving a parallel beam
 monochromatic x-ray source.

 This instrument description doesn't make sense.

 Regards,

 Jim


  The receiving side has Soller slits and a
 Tl-doped NaI point detector. I am trying to teach myself how to use
 TOPAS to PROPERLY analyze my data using Rietveld refinement
 techniques.

 I have recently taken a scan of the NIST line profile 660 LaB6
 standard followed by scans of my perovskite powders using a step size
 of 0.02 degrees and scan time of 4 seconds.

 Most of the articles I have read are specific to convergent/divergent
 beam geometries and I do not know how much of that information
 transfers to parallel beam geometries. If anyone could help me answer
 the following questions I would greatly appreciate it. These questions
 mainly address which parameters should be refined with the LaB6
 standard when using parallel beam geometry.
 1.      I need to use the scan of the LaB6 powders to characterize the
 contributions of the instrument to the diffraction profile. Starting
 with the emission profile, TOPAS asks for the wavelength, the Area,
 and the Lorentz Half Width. First, I assume the wavelength I should be
 the more recent Cu Ka wavelength of 0.154059 nm instead of 0.154056
 nm. Second, does Cu Ka have a definite Lorentz HW and “Area” or should
 these parameters be refined with the LaB6 diffraction pattern?
 2.      Since I have a Ge monochromater I assume the Lorentz polarization
 factor should be fixed at 27.3 (Is this correct?). Obviously the
 lattice parameters and atomic positions would be fixed.
 3.       I read that you should NOT refine both the zero shift error and
 sample displacement, and since it is parallel beam I only refine the
 zero shift error. Should I refine surface roughness, absorption, or
 sample tilt with the LaB6? (Currently I do not refine these)
 4.      Am I correct in assuming that I do not have any EQUITORIAL
 convolutions (e.g. from slits, FDS, beam spill, VDS) since it is
 parallel beam geometry? What about TUBE TAILS?
 5.      I am using the Finger_et_al  method to refine the AXIAL
 convolutions, however I often get a large error associated with the S
 value (sample length), even when my GOF is decent (1.45). Do any of
 you know why this would happen?
 6.      Should I refine the “Scale” or scale factor. (Currently I do)
 7.      IMPORTANT: Originally I was refining the crystallite size but it
 always refined to a very small value (~300nm), where as NIST claims
 660 LAB6 should have a mean grain size of a few microns or more. I
 assume this happens because the TOPAS is accounting for instrument
 caused peak broadening by making the crystallite size smaller than it
 actually is in the software. However, when I do refine the grain size
 I do get a better fit. Should I leave this unchecked, refine it, or
 fix it at a reasonable value of ~2500 nm.

 In summary, currently I am only refining the Lorentz HW and “Area” in
 the emission profile, zero shift error, the Finger parameters (S  H),
 the scale factor, and nothing else.
 I am unsure if I should be refining anything else such as the
 crystallite size, tube tails and other forms of equatorial
 convergence, or if there is something else that is important which I
 am disregarding completely. I am also unsure if I am correct in
 refining Lorentz HW and area in the emission profile.
 Sorry if I got a little long winded; I just wanted to give enough
 detail so people could answer. Thank you in advance for your help.

Re: Rietveld Neophyte

[Leonid Solovyov]

Dear Dave,

Actually, GSAS is not the best choice for crystal size analysis. There are 
specialized programs for this purpose such as MAUD for instance.

If you can’t refine the Gaussian broadening parameters GU GV and GW you may get 
them from the refinement for a standard with big (1000 nm) crystallites in 
order to allow for the instrumental broadening. Then you should refine not only 
LX, but also LY parameter responsible for the strain broadening. If you are 
lucky enough to refine LX without strong correlations with LY, background and 
other parameters, you may get an estimation of the crystallite size from the 
expression given in chapter ‘Interpretation of CW powder profile coefficients’ 
of GSAS manual. However, for “horrible data with very broad peaks of very low 
intensity” you may get misleading results due to incorrect separation of size, 
strain, and instrumental broadening contributions.

Best regards,
Leonid

***
 Leonid A. Solovyov
 Institute of Chemistry and Chemical Technology
 660049, K. Marx 42, Krasnoyarsk, Russia
 www.icct.ru/eng/content/persons/Sol_LA
 sites.google.com/site/solovyovleonid
***

--- On Fri, 10/23/09, David Weston david.wes...@nottingham.ac.uk wrote:

 From: David Weston david.wes...@nottingham.ac.uk
 Subject: Rietveld Neophyte
 To: Rietveld_l@ill.fr
 Date: Friday, October 23, 2009, 10:27 AM
 
 Hello,
 
 I have been using the GSAS software to analyse some XRD
 data from MgH2
 samples that have been heavily milled.  
 One piece of information I would like to assertain is the
 mean particle
 size of my powders.  The powders are of the order of
 10 nm by TEM.  
 Some relevant information;
 I am using a type 2 profile function.
 My data is horrible with very broad peaks of very low
 intensity.  
 I have had to set the GU GV and GW parameters in order to
 do anything at
 all. If I let them float then I lose any semblance.  
 I get a Chi2  1.
 
 My question is this;
     How do I obtyain the particle
 size?  
 
 Is it the LX parameter and is this measured in Angstroms?
 
 I hope someone will be kind enough to help me out of this
 mire!
 
 Regards
 
 Dave Weston 
 Research Fellow
 Department of M3 
 Wolfson Building
 University of Nottingham
 



  

Re: RE: Rietveld: U,V,W

[Davor Balzar]

As Maxim says, strain-related parameters are U and Y. By the same token, 
size-related parameters are P and X (both go with 1/cos(Theta). The reason is 
that this Rietveld model (the so-called TCH) assumes a Voigt function for both 
size and strain profile and therefore has to have both Lorentzian and Gaussian 
components. 

When refining the parameters, one has to keep in mind that instrumental 
broadening in general depends on the same parameters. Therefore, first refine 
all profile parameters on the diffraction pattern of the standard sample (as 
Brian said, LaB6 or similar) and then refine ONLY four parameters (U,P,X,Y) for 
the sample of interest, as far as instrumental conditions stay the same. 

More details and how to calculate size and strain from U,P,X, and Y were 
published in JAC 37 (2004) 911-924. The reprint and original data from seven 
different instruments (including synchrotron and neutron) can be found at 
http://mysite.du.edu/~balzar/s-s_rr.htm.

Davor BalzarUniversity of Denverwww.du.eduwww.du.edu/~balzar

- Original Message - 
From: Maxim V. Lobanov [EMAIL PROTECTED] 
Date: Sunday, November 30, 2008 10:37 pm 
Subject: RE: Rietveld:  U,V,W 
To: rietveld_l@ill.fr 


 Dear colleagues, 
  
   
  
  one question on that: 
  
   
  
  U and W should be instrumental constants that will not change with sample, 
  while V can have both an instrumental and a residual stress component. 
  
  as far as I understand, the strain broadening term should have FWMM~theta 
  dependence, i.e. Lorentzian Y in standard (GSAS) notation. 
  
  For the Gaussian part you have 
  
  FWHM^2=U*tan^2(th)+V*tan(th)+W+P/cos^2(th) 
  
  and the term that varies roughly as ~theta is U, not V. 
  
  Therefore, based on that and probably erroneously, I used to refine U 
  parameter rather than V (+ P, X, Y, of course). 
  
   
  
  I am wondering if somebody could make this more clear? 
  
   
  
  FullProf might be a bit more stable, but I think the process there 
 is about 
  the same. (BTW, if anyone works out how to convert GSAS profile 
 terms to 
  ones used in FullProf, I'd be interested to get those relationships into 
  CMPR; I am not sure if the scaling is only between centidegrees**2 and 
  degrees**2.) 
  
  So far I noticed that Fullprof uses interchanged (v.r.t. GSAS) XY, 
 i.e. X 
  corresponds to strain term there. There might be also other 
 differences, of 
  course... 
  
   
  
   
  
  Sincerely, 
  
  Maxim. 
  
   
  
  From: Brian H. Toby [mailto:[EMAIL PROTECTED] 
  Sent: Monday, December 01, 2008 5:21 AM 
  To: May, Frank 
  Cc: rietveld_l@ill.fr 
  Subject: Re: Rietveld: U,V,W 
  
   
  
  What is the correct procedure for refining U,V,W?  It is my understanding 
  that those parameters are a function of instrument geometry.  Does 
 one use a 
  standard material to determine U,V,W and then fix their values for the 
  instrument you're using?or do the values of U,V,W change 
 depending on 
  the sample being examined?  If so, why do the values change? 
  
   
  
  The GSAS manual covers the latter part of you questions pretty well, 
 though 
  perhaps indirectly. In theory, U and W should be instrumental 
 constants that 
  will not change with sample, while V can have both an instrumental 
 and a 
  residual stress component. However, this assumes that one also 
 refines a 
  crystallite size parameter, P when needed, which many people (myself 
  included) do not. In that case, U, V  W will all change to 
 compensate for 
  crystallite broadening. 
  
   
  
  I do recommend using a standard with good sharp peaks (SRM LaB6 is the 
  ideal, though there are likely to be many other oxides handy that work 
  reasonably.) If you can't get a good fit to your standard, then you 
 do not 
  want to advance to an unknown until you understand the problems with 
 your 
  instrument/technique. 
  
   
  
  Where possible, I try to start a refinement with values that are 
 close to 
  correct for U, V  W (+ X  Y where significant) and put off refining 
 them 
  until late in the refinement, when they tend to be pretty stabile. 
  Initially, I usually refine U, V  W together and then refine X and 
 then Y 
  solo and then finally in combinations until everything is refined together. 
  Look for parameters that are refining to zero and turn them off, 
 since GSAS 
  does not deal with that very well. Also look at the widths vs 2theta 
  (widplt) to see if the functions are reasonable. 
  
   
  
  The routine in CMPR for fitting U, V  W values to a set of peak 
 widths has 
  been useful for me where I don't have good calibration information 
 for an 
  instrument. 
  
   
  
  FullProf might be a bit more stable, but I think the process there is 
 about 
  the same. (BTW, if anyone works out how to convert GSAS profile terms 
 to 
  ones used in FullProf, I'd be interested to get those relationships into 
  CMPR; I am not sure if the scaling is only between centidegrees**2 and 
  degrees**2

Re: Rietveld: U,V,W

[Jim Cline]

Hi,

Self Citation: NIST Standard Reference Materials for 
Characterization of Instrument Performance Industrial Applications 
of X-ray Diffraction Ed by F. H. Chung  D. K. Smith, pp 903-917.  A 
pdf is available; email to request.


In this I outline how I use SRM 660 (it was 660 in 2000, then it was 
660a until ~July '07, we are working on 660b) for qualifying and 
characterizing instrument performance with both profile fitting and 
the Rietveld method, via GSAS.  I suggest obtaining a set of TCH 
parameters with LaB6.  The instrument specific ones thereafter 
remained fixed while the other are used as a floor for refined 
values.  With this approach I was able to obtain stable and 
meaningful results from laboratory equipment.


Regards,

Jim

At 08:25 PM 11/30/2008, you wrote:

To all:

What is the correct procedure for refining U,V,W?  It is my 
understanding that those parameters are a function of instrument 
geometry.  Does one use a standard material to determine U,V,W and 
then fix their values for the instrument you're using?or do the 
values of U,V,W change depending on the sample being examined?  If 
so, why do the values change?


Thanks in advance.

Frank May



From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Sun 11/30/2008 1:32 PM
To: rietveld_l@ill.fr
Subject: Re: I am a newcome, how can I begin my rietveld refinement analysis



Hi, Li:

To me, the most wonderful tool to determine initial peakshape parameters is
CMPR.
CMPR is especially oriented to GSAS and gives you GU, GV, GW etc. And when
you use EXPGUI for GSAS, you can also try Graphs-widplt to see how FWHM
develops when parameters are tuned.
When you prefer Fullprof, you should take a factor to get U, V, W etc. i am
not sure about the facor exactly, maybe GX~100X(X=U, V, W), er..? Anyway,
just go ahead and make a try.

Faithfully
Jun Lu
--
Lst. Prof. Lijie Qiao
Department of Materials Physics and Chemistry
University of Science and Technology Beijing
100083 Beijing
P.R. China
http://www.instrument.com.cn/ilog/handsomeland/


James P. Cline
Ceramics Division
National Institute of Standards and Technology
100 Bureau Dr. stop 8520 [ B113 / Bldg 217 ]
Gaithersburg, MD 20899-8523USA
[EMAIL PROTECTED]
(301) 975 5793
FAX (301) 975 5334 

Re: Rietveld: U,V,W

[Brian H. Toby]

What is the correct procedure for refining U,V,W?  It is my  
understanding that those parameters are a function of instrument  
geometry.  Does one use a standard material to determine U,V,W and  
then fix their values for the instrument you're using?or do the  
values of U,V,W change depending on the sample being examined?  If  
so, why do the values change?



The GSAS manual covers the latter part of you questions pretty well,  
though perhaps indirectly. In theory, U and W should be instrumental  
constants that will not change with sample, while V can have both an  
instrumental and a residual stress component. However, this assumes  
that one also refines a crystallite size parameter, P when needed,  
which many people (myself included) do not. In that case, U, V  W  
will all change to compensate for crystallite broadening.


I do recommend using a standard with good sharp peaks (SRM LaB6 is  
the ideal, though there are likely to be many other oxides handy that  
work reasonably.) If you can't get a good fit to your standard, then  
you do not want to advance to an unknown until you understand the  
problems with your instrument/technique.


Where possible, I try to start a refinement with values that are  
close to correct for U, V  W (+ X  Y where significant) and put off  
refining them until late in the refinement, when they tend to be  
pretty stabile. Initially, I usually refine U, V  W together and  
then refine X and then Y solo and then finally in combinations until  
everything is refined together. Look for parameters that are refining  
to zero and turn them off, since GSAS does not deal with that very  
well. Also look at the widths vs 2theta (widplt) to see if the  
functions are reasonable.


The routine in CMPR for fitting U, V  W values to a set of peak  
widths has been useful for me where I don't have good calibration  
information for an instrument.


FullProf might be a bit more stable, but I think the process there is  
about the same. (BTW, if anyone works out how to convert GSAS profile  
terms to ones used in FullProf, I'd be interested to get those  
relationships into CMPR; I am not sure if the scaling is only between  
centidegrees**2 and degrees**2.)


Brian


Brian H. Toby, Ph.D.office: 630-252-5488
Materials Characterization Group Leader, Advanced Photon Source
9700 S. Cass Ave, Bldg. 433/D003 work cell: 630-327-8426
Argonne National Laboratory secretary (Marija): 630-252-5453
Argonne, IL 60439-4856 e-mail: brian dot toby at anl dot gov

Re: Rietveld: U,V,W

[Mingtao Li]

Why my reply went to the author's personal mail box? I am very sorry for that.

Now I am hunting for a standard reference material to determine the
profile parameters of our instrument X'pert Pro.

-- 
Mingtao Li
State Key Laboratory of Multiphase Flow in Power Engineering
School of Energy and Power Engineering
Xi'an Jiaotong University
Xi'an, 710049
P.R.China
Tel: +86-29-8266 8296
Fax: +86-29-8266 9033
Email: [EMAIL PROTECTED]

RE: Rietveld: U,V,W

[Maxim V. Lobanov]

Dear colleagues,

 

one question on that:

 

U and W should be instrumental constants that will not change with sample,
while V can have both an instrumental and a residual stress component.

as far as I understand, the strain broadening term should have FWMM~theta
dependence, i.e. Lorentzian Y in standard (GSAS) notation.

For the Gaussian part you have

FWHM^2=U*tan^2(th)+V*tan(th)+W+P/cos^2(th)

and the term that varies roughly as ~theta is U, not V.

Therefore, based on that and probably erroneously, I used to refine U
parameter rather than V (+ P, X, Y, of course).

 

I am wondering if somebody could make this more clear?

 

FullProf might be a bit more stable, but I think the process there is about
the same. (BTW, if anyone works out how to convert GSAS profile terms to
ones used in FullProf, I'd be interested to get those relationships into
CMPR; I am not sure if the scaling is only between centidegrees**2 and
degrees**2.) 

So far I noticed that Fullprof uses interchanged (v.r.t. GSAS) XY, i.e. X
corresponds to strain term there. There might be also other differences, of
course...

 

 

Sincerely,

Maxim. 

 

From: Brian H. Toby [mailto:[EMAIL PROTECTED] 
Sent: Monday, December 01, 2008 5:21 AM
To: May, Frank
Cc: rietveld_l@ill.fr
Subject: Re: Rietveld: U,V,W

 

What is the correct procedure for refining U,V,W?  It is my understanding
that those parameters are a function of instrument geometry.  Does one use a
standard material to determine U,V,W and then fix their values for the
instrument you're using?or do the values of U,V,W change depending on
the sample being examined?  If so, why do the values change?

 

The GSAS manual covers the latter part of you questions pretty well, though
perhaps indirectly. In theory, U and W should be instrumental constants that
will not change with sample, while V can have both an instrumental and a
residual stress component. However, this assumes that one also refines a
crystallite size parameter, P when needed, which many people (myself
included) do not. In that case, U, V  W will all change to compensate for
crystallite broadening. 

 

I do recommend using a standard with good sharp peaks (SRM LaB6 is the
ideal, though there are likely to be many other oxides handy that work
reasonably.) If you can't get a good fit to your standard, then you do not
want to advance to an unknown until you understand the problems with your
instrument/technique. 

 

Where possible, I try to start a refinement with values that are close to
correct for U, V  W (+ X  Y where significant) and put off refining them
until late in the refinement, when they tend to be pretty stabile.
Initially, I usually refine U, V  W together and then refine X and then Y
solo and then finally in combinations until everything is refined together.
Look for parameters that are refining to zero and turn them off, since GSAS
does not deal with that very well. Also look at the widths vs 2theta
(widplt) to see if the functions are reasonable. 

 

The routine in CMPR for fitting U, V  W values to a set of peak widths has
been useful for me where I don't have good calibration information for an
instrument. 

 

FullProf might be a bit more stable, but I think the process there is about
the same. (BTW, if anyone works out how to convert GSAS profile terms to
ones used in FullProf, I'd be interested to get those relationships into
CMPR; I am not sure if the scaling is only between centidegrees**2 and
degrees**2.) 

 

Brian

 

 

Brian H. Toby, Ph.D.office: 630-252-5488

Materials Characterization Group Leader, Advanced Photon Source

9700 S. Cass Ave, Bldg. 433/D003 work cell: 630-327-8426 

Argonne National Laboratory secretary (Marija): 630-252-5453

Argonne, IL 60439-4856 e-mail: brian dot toby at anl dot gov 







 

RE: Rietveld: U,V,W

[Leonid Solovyov]

Brian wrote:
U and W should be instrumental constants that will not change with sample, 
while V can have both an instrumental and a
residual stress component.

Maxim wrote:
as far as I understand, the strain broadening term should have FWMM~theta 
dependence, i.e. Lorentzian Y in standard (GSAS) notation.
For the Gaussian part you have
FWHM^2=U*tan^2(th)+V*tan(th)+W+P/cos^2(th)
and the term that varies roughly as ~theta is U, not V.
Therefore, based on that and probably erroneously, I used to refine U 
parameter rather than V (+ P, X, Y, of course).
I am wondering if somebody could make this more clear?

Dear Brian and Maxim,

In fact, the term responsible for the Gaussian strain component is U, not V.

Regards,
Leonid

***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
www.icct.ru/eng/content/persons/Sol_LA
www.geocities.com/l_solovyov
***


  

RE: Rietveld Round Robin Test

[Ian.Madsen]

Title: Message



There 
were two papers resulting from a round robin on quantitative phase analysis 
sponsored by the IUCr Commission on Powder Diffraction. They 
are:-

(1) I.C. Madsen, N.V.Y. 
Scarlet, L.M.D. Cranswick, T. Lwin, J. Appl Cryst. (2001) 34, 409-426
(2) N.V.Y. Scarlet, 
I.C. Madsen, L.M.D. Cranswick, T. Lwin, E. Groleau, G. Stephenson, M. Aylmore, 
N. Agron-Olshina, J. Appl Cryst. (2002) 35, 383-400The second paper 
deals with the more complex phase systems. If you do not have access to 
J.Appl.Cryst. let me know and I will send reprints.
During 
the design of the round robin we contemplated using cement materials but were 
concerned about the long-term stability of 
clinker

 
Cheers

o--oo0oo---o
 Ian Madsen
CSIRO 
Minerals
  Box 312
 Clayton South 
3169
 Victoria
 AUSTRALIA
  Phone +61 3 9545 8785 
direct
 
 
+61 3 9545 8500 switch
 
 +61 (0) 
417 554 935 mobile
 FAX +61 3 9562 
8919
 Email [EMAIL PROTECTED] 
o--oo0oo---o

  
  -Original Message-From: 
  [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Wednesday, 
  8 June 2005 7:18 PMTo: Rietveld Mailing ListSubject: 
  Rietveld Round Robin TestFellow rietvelders, Is 
  there any round robin test (official or not) for Rietveld? I am particularly 
  interested in cement and clinker phase refinement. Thank you. John KaragiannisHellenic Cement Research Center Ltd. \ 
  Microstructure DeptK. Pateli 15ATHENS ATTICA 141 23GREECEFax: 
   0030-210-2842140Tel:  0030-210-2818453===The 
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Re: rietveld refinement

[Nicholas Armstrong]

Hi,
At the moment there is development of a NIST Nanocrystallite Size Standard 
Reference Material (SRM1979).

Jim Cline and I are working on this SRM. It will include two materials:
(1) CeO2 with spherical crystallite shape and size distribution in the ~20nm 
size range (isotropic shape);
(2) ZnO with cylindrical or hexagonal prismatic crystallite shape with height 
in the, H~60-80nm and diameter, D~20-30nm range (anisotropic shape).

This outlined in introduction of Armstrong et al (2004b) chapt.8, in 
Diffraction analysis of the microstructure of materials, Springer-Verlag, 
pp.187--227.

In both cases the Bayesian/MaxEnt method will be used to determine the 
*physical* size distribution and shape. For example in the case of (1), the 
method tests the model for a spherical crystallite shape, while also testing 
various size distribution models i.e lognormal, gamma etc. For this case a 
lognormal size distribution has found to be the appropriate distribution. In 
the case of (2) the distributions are for H and D, respectively, while testing 
different shape models can also be carried out. This presently being developed.

The Bayesian/MaxEnt method is a general formulation which tests the underlying 
assumption of various models and determines the most probable size distribution 
and crystallite shape.

There is lots of working/development going on!!
Regards, Nicholas


- Original Message -
From: Nicolae Popa [EMAIL PROTECTED]
Date: Monday, November 22, 2004 7:12 pm

 
 
  It is also true that no development has been done for anisotropy. 
 Not yet!
 
  Well, if all previous works about trying to take account of 
 size/strain anisotropy in the Rietveld method are nothing yet, 
 this allows to
  close the discussion. Let us wait for really serious developments to
  come.
 
 You not correctly understood me (I would like to believe that not
 ill-disposed).
 I said that no development for size anisotropy has been done including
 physical size distributions (like lognormal, etc.) as were done 
 for the
 isotropic case.
 For example: Langford, Louer  Scardi, JAC (2000) 33, 964-974 and 
 Popa 
 Balzar JAC (2002) 35, 338-346.
 Concerning previous (phenomenological) works trying to take account of
 strain/size anisotropy in the Rietveld method, I have myself a 
 contribution:The (hkl) dependence of diffraction-line broadening 
 caused by strain and
 size for all Laue groups in Rietveld refinement, N. C. Popa, J. 
 Appl. Cryst.
 (1998) 31, 176-180.
 Could I be so stupid to say that such kind of works, including 
 mine, are
 nothing?
 
 Best wishes,
 Nicolae Popa
 
 
 
 
 
 


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Re: rietveld refinement

[Matteo Leoni]

just my 2 cents...

 Could I be so stupid to say that such kind of works, including mine, are
 nothing?
  
following Nicolae, I should also add to the list myself as well as most 
people participating to the four editions of the size-strain 
conference/meeting/workshop and all participants to Davor's size-strain  
round-robin.

I bet people should spend more time in the library... this is the point.
This is also a self criticism as I'm not the best library addict (though,  
online resources has simplified life enormously)... 

We should not try to use line profile analysis methods as a black box: 
it is easy to obtain numbers from measured data (with a proper software a 
computer can do it automatically), but then it is in the ability of the 
scientist to attach them a proper physical meaning.
What it is difficult (perhaps impossible?) is willing and pretending to do 
it in the general case as we're dealing with something that has no precise 
rules (domain size, shape and their distributions are not properties of 
the materials, nor they can be easily predicted in advance).
Some simple cases have been studied and some references already posted by 
several people in here, and in most of them the agreement between 
diffraction and alternative techniques is quite good: just in few cases, 
though, enough information is available to interpret the strain broadening 
fully in terms of physical defects present in the material, or to model 
the size term using a more or less complex distribution of (iso-shape) 
domains. But also in those cases the result is the one compatible with the 
model assumptions and does not pretend to be God's truth.

So welcome the round robin on a more complex sample to test the maturity 
of the algorithms (they should be even tested on simpler examples, as 
concluded on the latest size-strain conference, but that's another 
story..), but beware that without any a priori info (or with a wrong 
one!), a vast set of odd results can be obtained. As a comparison, it 
would be like pretending to do a search match, a structure solution or,  
even worse, a Rietveld refinement on a material for which we don't know  
any chemical information... 

Going back to Leonid's question, well the answer is easy: check the 
premises... the assumptions behind the use of the TCH function are not 
compatible with he presence of a lognormal distribution of domains. It can 
be proven mathematically that the Fourier coefficients for a profile 
describing a lognormal distribution of domains have a hook at low Fourier 
number, hook that cannot be reproduced by any whatsoever voigtian or 
voigtian-like curve. This is a common problem in the use of Voigt and 
voigt-like curves in describing the peak profiles from nanocrystalline 
powders and is also the main source of the superlorentzian peak tails 
(they are a trick to get rid of the physical information contained in the  
profile ;) we are a bit masochist, aren't we?)

Best regards
Mat


-- 
Matteo Leoni
Department of Materials Engineering and Industrial Technologies 
University of Trento
38050 Mesiano (TN)
ITALY
Tel +39 0461 882416e-mail:   [EMAIL PROTECTED]
Fax +39 0461 881977Web:   www.matteoleoni.ing.unitn.it

Re: rietveld refinement

[Nicolae Popa]

 So I cannot let say that Significantly different physical
 size distributions could describe equally well the peak profile.
 This is confusing. You may say that : significantly different
 crystallite shapes could describe equally well the peak profile
 in cubic symmetry. I am not sure that this sentence is
 valuable equally for other symmetries when looking at all

Sorry, it seems me that rather your sentence is confusing, not mine.

In the example with CeO2 the crystallites are quite spherical
(one shape) even seen by microscope. But two significantly different
distributions of the
sphere radius (6a1, 6a2) (lognormal  gamma, respectively) given quite the
same column length distribution
(6b1, 6b2) and practically the same peak profile. It is no matter here of
different crystallite shapes because the shape is unique (sphere). And also
the cubic symmetry has no relevance, this should happen for any symmetry (I
mean not an unique solution for the sphere radius distribution).
(By the way, the sample of CeO2 in discussion is just the sample used in the
round-robin paper that you co-authored; in this last paper we used only the
lognormal distribution, but doesn't mean that this is the unique solution
from powder diffraction).

Concerning the different crystallite shapes, this is another storry. I said
that even if the cristallites are not spherical, it is not obligatory to
observe an anisotropic size broadening effect. Not spherical crystallites is
only the necessary condition for size anisotropy effect, but not sufficient.
The anisotropic size broadening effect is observable only if the non
spherical shape is preferentially orientated with respect to the crystal
axes (don't confuse with the texture). It is the case of your nickel
hydroxyde in which the plate-like normal is preferentially oriented along
the hexagonal c axis. But, if the not spherical crystallite shapes are
randomly oriented with respect to the crystal axes (which is possible) the
size broadening effect is isotropic and, only from powder diffraction, we
can conclude erroneously that the crystallites are spherical.
On the other hand, if the anisotropy is observed, the crystallite shape (and
the distributions of specific radii) can not be uniquely determined only
from powder diffraction. What we can determine is an apparent shape (and
column lengths averages). Has any sense, in this case, to search for so
called physical models, or we have to be content with phenomenological
findings (so much blamed, at least implicitely)? It is only a question,
valid also for the strain effect.


 So, let us have more fun with a size strain round robin on some
 complex sample  (or even a size-only round robin not on a
 cubic compound ;-).

I agree entirely.

Best wishes,
Nicolae Popa

Re: rietveld refinement

[Nicolae Popa]

Title: RE: rietveld refinement





  Doesn't help with a size 
  distribution, as it only works well for a relatively monodisperse material - 
  but it does work under some circumstances.
  Pam 
  
  I disagree, it works also 
  for large dispersion. One example you can find in JAC (2002) 35, 338-346, 
  "Sample 2". It is true that the specific peak profile (that can be 
  "superlorentzian") can not be found in no available Rietveld code. It is also 
  true thatno development has been done for anisotropy. Not 
  yet!
  
  Best wishes,
  Nicolae 
Popa

Re: rietveld refinement

[Armel Le Bail]

It is also true that no development has been done for anisotropy. Not yet!
Well, if all previous works about trying to take account of size/strain
anisotropy in the Rietveld method are nothing yet, this allows to
close the discussion. Let us wait for really serious developments to
come.
Armel
  

Re: rietveld refinement

[Whitfield, Pamela]

Title: RE: rietveld refinement





I'm afraid that you got the wrong end of the stick -I wasn't talking about the application of peak broadening to size distribution, I was commenting that determining crystallite shape is perfectly possible (some comments were flying that said otherwise), and I've done it myself. For that purpose a sample approaching monodisperse is helpful. It would be a bit pointless trying to determine the size distribution of a monodisperse sample !! :-)

I did send an email that I think only went to Armel by mistake making this clearer. I was having a slow morning! :-)


Pam 


-Original Message-
From: Nicolae Popa
To: [EMAIL PROTECTED]
Sent: 11/21/2004 5:04 AM
Subject: Re: rietveld refinement





Doesn't help with a size distribution, as it only works well for a
relatively monodisperse material - but it does work under some
circumstances.
Pam 

I disagree, it works also for large dispersion. One example you can find
in JAC (2002) 35, 338-346, Sample 2. It is true that the specific peak
profile (that can be superlorentzian) can not be found in no available
Rietveld code. It is also true that no development has been done for
anisotropy. Not yet!

Best wishes,
Nicolae Popa

RE: rietveld refinement

[Mutta Venkata Kamalkar (pBSc)]

can you please send me the soft copy of the paper you referred to. We don't
have access to that journal...

very much sincerely yours
venkat

From: Armel Le Bail [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Fri, 19 Nov 2004 16:49:42 +0100

 I'd have to disagree on this point - troublemaker I suppose!  I've 
 followed the work by Langford and Louer closely, and have successfully 
 applied their techniques
 
 I do not understand on what point exactly you disagree.
 The cited paper about size effect in nickel hydroxyde
 is co-authored by D. Louer, and may still seem kosher to him ;-).
 The full reference is :
 
 A. Le Bail and D. Louër. J. Appl. Cryst. (1978). 11, 50-55
 [doi:10.1107/S0021889878012662]
 Title: Smoothing and validity of crystallite-size distributions from 
 X-ray line-profile analysis Abstract: A smoothing procedure is 
 described which eliminates spurious details on crystallite-size 
 distribution functions deduced from X-ray line profiles. It is based 
 on a least-squares process with a stabilization scheme and is 
 applied to composite specimens prepared by mixing known quantities 
 of samples of nickel hydroxide, whose crystallite size-distribution 
 functions were previously determined. Calculated and observed 
 distributions and average sizes are compared. The results are 
 reasonably good and show the self-consistency of the method.
 
 Best regards,
 
 Armel
--- End of Original Message ---

Re: rietveld refinement

[Mutta Venkata Kamalkar (pBSc)]

can anyone send me a soft copy of the following paper
J. Appl. Cryst. (1978). 11, 50-55.


thanks 
venkat

+++
M Venkata Kamalakar
Junior Research Fellow,
S.N.Bose.National Centre for Basic Sciences,
Block-JD, Sector-3, Salt Lake,
Kolkata, Pin: 700 098.
Phone no: 033 23355705/6/7/8 Extn: 404, 104, 301.
+++

-- Original Message ---
From: Armel Le Bail [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Fri, 19 Nov 2004 08:43:11 +0100

 It is a separate question to what extent those distributions are
 physical...
 
 Simple attempts to establish that at least the size distributions
 obtained from a mixture of two samples with same composition
 and two very different size distributions, are close to the
 expected result, establishing some self-consistency of the
 methodology, if not that they are physical (I believe they are
 physical in case of size-only effect).
 
 See for instance J. Appl. Cryst. (1978). 11, 50-55.
 This can be found also (in french) in a thesis :
 http://tel.ccsd.cnrs.fr/documents/archives0/00/00/70/41/index_fr.html
 (self citation...;-). Things have not changed a lot since these
 old times.
 
 Armel
--- End of Original Message ---

Re: rietveld refinement

[Nicolae Popa]

 methodology, if not that they are physical (I believe they are
 physical in case of size-only effect).

The diffraction alone can not decide. Significantly different physical
size distributions could describe equally well the peak profile
(J.Appl.Cryst. v35 (2002) 338-346 - self citation too).

Nicolae Popa

Re: rietveld refinement

[Armel Le Bail]

The diffraction alone can not decide. Significantly different physical
size distributions could describe equally well the peak profile
(J.Appl.Cryst. v35 (2002) 338-346 - self citation too).
Nicolae Popa
Looking at your figures 6b1 and 6b2, I measure how we
differ on the sense of significantly different. As you comment
in the text, The curves 1 and 2 differ in the position of the
maximum by only 2 A and in height of the maximum by
9.76%.
I would not call that significantly different but very similar.
Armel

Re: rietveld refinement

[Nicolae Popa]

 The diffraction alone can not decide. Significantly different physical
 size distributions could describe equally well the peak profile
 (J.Appl.Cryst. v35 (2002) 338-346 - self citation too).
 Nicolae Popa

 Looking at your figures 6b1 and 6b2, I measure how we
 differ on the sense of significantly different. As you comment
 in the text, The curves 1 and 2 differ in the position of the
 maximum by only 2 A and in height of the maximum by
 9.76%.

 I would not call that significantly different but very similar.

 Armel

Yes, but the figure 6b represents the COLUMN LENGTH distribution not the
CRYSTALLITE RADIUS distribution (in this case of spherical crystallites).
The crystallite radius distributions are given in 6a1 and 6a2 (lognormal and
gamma, respectively) and they are significantly different, what can be seen
also in the table 1: the average radius and the dispersions are completely
different. Nevertheless the profile of the diffraction peak is equaly well
described. And the column length distribution is quite the same (as
discussed in text and as you observed). But when we are speaking about the
physical model we understand in fact the distribution of the crystallite
radius (if spherical). Is that lognormal or gamma? Is the average radius
90(6) or 69(1) Angstroms, is the parameter c (determining the dispersion)
0.18 or 0.39?  We can not say only from diffraction that one is more
physical than other. On the other hand is the column length distribution a
full physical description of the crystallites, I mean of the shape and
radius (radii) distribution? I think not. You can imagine, for example, that
the crystallites are even not spherical, but ellipsoidal. It is easy to
understand that if the Euler angles representing the orientations of the
ellipsoidal principal axes with respect to the crystal axes are UNIFORMLY
distributed in their domains of definition, will be NO anisotropy effect.
Then we can think the crystallite are spherical with a certain distribution
of radius, when in fact they are ellipsoidal with other distributions of
(three) radii. But the column length distribution (and the peak profile) is
the same. What we see in diffraction is the column lengths (volume  area
averaged) and the classics were not full ignoring the shape and radius
(radii) distribution(s).

Nicolae Popa (Mister, Messieur, Don, Dom, etc.)

Re: rietveld refinement

[Armel Le Bail]

What we see in diffraction is the column lengths (volume  area
averaged) and the classics were not full ignoring the shape and radius
(radii) distribution(s).
Nicolae Popa (Mister, Messieur, Don, Dom, etc.)
Of course I agree with you that completely different shapes
may correspond to the same distribution of column length.
For diffraction, and considering one direction, the columns of
cells look exactly as if they were separated. So, obviously :
   |--|
   |  |--|
   |  |  |--|--|
   |--|--|--|--|
gives the same column length distribution as :
   |--|
   |  | |--|
   |  |--|--|  |
   |--|--|--|--|
or as separated columns :
   |--| [--|
   |  | |  |
   |  | |  | |--|  |--|
   |--| |--| |--|  |--|
or etc, taking the columns in the bottum-up sense.
But, with these 3 different models (and more are possible), you
would not have the same distribution of column lengths in the
orthogonal direction...
My problem with most recent papers about size effect is that
they always consider cubic compounds, possibly spherical
crystallites etc. In such a case, all directions are gathered in
one.
Could you study something more complex sometimes ?
In my self-citation work, the study was made on nickel
hydroxyde, with hexagonal structure, looking for columns
exclusively in the direction of the c axis, using the Bertaut
formulations, with careful extraction of the column lenght
distribution after deconvolution from the instrumental effect.
There was a strong size anisotropy. The X-ray study cannot
gives the shape (you see that I agree with you on that point),
an electron microscopy study showed that the coherently
diffracting domains are plate-like crystallites aggregated along
the c axis.
So I cannot let say that Significantly different physical
size distributions could describe equally well the peak profile.
This is confusing. You may say that : significantly different
crystallite shapes could describe equally well the peak profile
in cubic symmetry. I am not sure that this sentence is
valuable equally for other symmetries when looking at all
profiles. You would have maybe to restrain to the consideration
in one direction : if no change is produced in all other directions,
what is the degree of freedom for the crystallite shape now ?
Is it possible to organize the columns differently in one
direction without changing also the peak profiles in all other
directions for a triclinic compound ?
So, let us have more fun with a size strain round robin on some
complex sample  (or even a size-only round robin not on a
cubic compound ;-).
Best
Armel

Re: rietveld refinement

[Armel Le Bail]

Small error, sorry,
three of the possible arrangement were :
   |--|
   |  |--|
   |  |  |--|--|
   |--|--|--|--|
   |--|
   |  | |--|
   |  |--|--|  |
   |--|--|--|--|
   |--|
   |  | |--|
   |  | |  | |--|  |--|
   |--| |--| |--|  |--|
Armel

RE: rietveld refinement

[Christopher Chervin]

Hi Venkat,

If you mean to use rietveld on X-ray data I don't think you can get 
particle size distributions.  X=ray data will give you an average 
crystallite size but this is not a distribution just an average.  Also, it 
is crystallite size and the actual particles size can be different if the 
crystallites are agglomerated.

Have you considered trying dynamic light scattering?  


Cheers,

Chris

will  
 
 I am a new user of rietveld softwares. Can anyone suggest me any program 
or
 software based on reitveld algorithm and giving the following results...
 
 1) size distribution of particles in a sample.
 
 
 yours sincerely
 venkat
 

Re: rietveld refinement

[Whitfield, Pamela]

This is where the real fun starts (if you're a masochist!).  I just finished
doing some work along those lines this afternoon, and managed to get it to
work(ish) eventually.  The double-Voigt analysis can give you Dv (volume
weighted domain size) and Ds (surface weighted domain size).  If you assume
a log-normal size distribution (not completely unreasonable) it is possible
to work backwards and derive the distribution from these values.  However,
you need really good data or you get complete rubbish because of the
correlations.  
Davor Balzar covers some of this in his recent J.Appl.Cryst. paper (page 911
latest issue) and Popa and Balzar, J.Appl.Cryst. v35 (2002) 338-346.  It
gave me a bit of a brain-ache but it does work!

Pam

Dr Pamela Whitfield CChem MRSC
Energy Materials Group
Institute for Chemical Process and Environmental Technology
Building M12
National Research Council Canada
1200 Montreal Road
Ottawa  ON   K1A 0R6
CANADA
Tel: (613) 998 8462 Fax: (613) 991 2384
Email: mailto:[EMAIL PROTECTED]
ICPET WWW: http://icpet-itpce.nrc-cnrc.gc.ca


-Original Message-
From: Maxim V. Lobanov [mailto:[EMAIL PROTECTED]
Sent: November 18, 2004 1:51 PM
To: [EMAIL PROTECTED]


What I remember is that Breadth outputs the distributions. What might
be the solution is to convert (write a program) Rietveld peak output
to Breadth input. However, I have never done this myself; I converted
Xfit-style
peak files only, which is pretty straightforward. 
It is a separate question to what extent those distributions are
physical...
Sincerely,
Maxim.
___
Maxim V. Lobanov [EMAIL PROTECTED]
Department of Materials Science and Engineering
University of Tennessee
101 South College
1413 Circle Dr.
Knoxville, TN 37996

RE: Rietveld refinement and PDF refinement ?

[Radaelli, PG (Paolo)]

 do you really have the 
 resolution even on
 HRPD to see the diffuse scattering between Bragg peaks at 
 high Q ?

No we don't, but this is not the main point (by the way, we don't use HRPD
for PDF, it doesn't go to sufficiently short wavelengths).  The main reason
to go to high Q is to avoid truncation errors.  If you truncate S(Q), all
your G(r) peaks will be convoluted with the Fourier transform of a step
function, which is a sinx/x function.  The width of the central peak is
roughly 1/Qmax.  If you use a wavelength of 0.5 A, this corresponds to about
0.08 A, or an equivalent B of 0.5.  This in itself can be a problem when you
want to look at sharp correlation features.  Even worse, the ripples will
propagate to adjacent PDF peaks, generating unphysical features.  There are
ways to suppress the ripples by convoluting the data with an appropriate
smooth function rather than truncating them (these are extensively used in
disordered materials work), but they all tend to broaden the features.  You
can also fit a model including the ripples (as in PDFfit) but it is clearly
better not to have them if you are trying to exploit the model independence
of PDF.  Going to high Q does not solve all the problems. If the high-Q data
are noisy, your truncation function will have higher frequency but also
higher (and random) amplitude in the ripples, so there is always a
compromise Qmax, depending on statistics.  Finally, very high-Q data are
quite difficult to normalise, because of the epithermal background.   


 You may
 get better temperature factors with high-Q PDF refinement, 
 but you will
 also do that with high-Q Rietveld.

Generally, all crystallographic parameters come out worse from PDF
refinements than from Rietveld on the same data sets.  I think this is
because you are trying to fit an average structure to something that
contains correlations, so the fit is bound to be worse.  You could fit a
correlated model, but then you would not get temperature factors in the
usual sense. 

 I also doubt that just because PDF uses data between the 
 Bragg peaks, then
 it must be superior for seeing details not centered on atoms 
 in real space
 in a crystal, eg the split atom sites in (In/Ga)As). You 
 might do just as
 well with Bragg scattering if you use the result of Rietveld 
 refinement to
 construct a Fourier map of the structure. Happily, a sampling of
 reciprocal space (Bragg peaks) is sufficient to re-construct 
 the entire
 density of a periodic structure in real space, not just point 
 atoms, to a
 resolution limited only by Q.

You are right.  PDF is not always superior.  It is the interpretation of the
Fourier density in terms of correlated displacements that emerges uniquely
from PDF, although you can often guess it right from the Fourier map in the
first place.  The case of Jahn-Teller polarons in manganites (La,Ca)MnO3 is
quite illuminating.  Several groups noticed that the high-temperature phase
(above the CMR transition) has large DW factors for O.  We showed that this
affects primarily the longitudinal component along the Mn-O bonds, and
guessed that this was caused by an alternation of short and long Mn-O
distances.  Simon Billinge showed the same thing quite convincingly from PDF
data.  Only the latter can be considered direct evidence (with some
caveats).

 But you do agree that in a PDF experiment you integrate over 
 energy, so
 you only see an instantaneous snapshot of the structure...

Yes, I agree with this and the fact that inelasticity corrections are an
issue.  Sometimes they are exploited to obtain additional information, and
there is a claim that one can measure phonon dispersions with this method,
but the issue is quite controversial.

 
 So while I am convinced of the interest of PDF for non-crystalline
 materials, with short or intermediate range order, I am not 
 yet convinced
 that you gain much from PDF refinement of crystalline 
 materials, where you
 can also apply Rietveld refinement.

I agree completely.  The directional information gained from phasing and the
fact of locking in to specific Fourier components is a major asset of
Rietveld analysis.  PDF is useful when correlated disorder is important (and
large), even if superimposed on an ordered structure.

Paolo Radaelli

RE: Rietveld refinement and PDF refinement ?

[Hewat Alan]

 Another reason which may preclude your self-convincing is the
 fact that all the very good PDF studies of materials... are
 not by using constant wavelength neutrons...

You are right Armel :-) About the current advantage of SR and TOF for PDF,
I mean. That is why I am interested in being convinced.

 So, this PDF advantage does not impress me a lot (like opening an
 already open door), EXAFS reveals the same.

Open doors are good, and open minds are even better :-)

Alan.

RE: Rietveld refinement and PDF refinement ?

[Armel Le Bail]

Adding 2 cents to the discussion...
But I will try to convince myself otherwise :-)
Another reason which may preclude your self-convincing is the
fact that all the very good PDF studies of materials that are not perfectly
crystallized (producing diffuse scattering), though not being amorphous,
are made by using synchrotron data or neutron data from spallation
sources : not by using constant wavelength neutrons...
In the past, I have studied a few glasses at ILL by using the D4
instrument, at 0.5 A wavelength, allowing to attain modestly high Q
values. The fact that the instrument resolution was very poor was not
a problem for amorphous materials, but it was a problem for crystalline
or partially crystalline materials : they also look like amorphous in the
reciprocal space, due to the quite large instrumental contribution to the
peak broadening. Is that improved now ? If not, you would not be
able to apply both the Rietveld and the PDF methods from the
same data, raw or Fourier transformed. The raw data would
be too bad for applying the Rietveld method. So, no PDF at ILL ?-).
A different question is about size/strain effects, possibly
anisotropic, which may have effects on the peak shapes
and peaks broadening. We can more or less (progress are to
be made), take account of these effects reflecting the deviation
of the real sample from a model of infinite perfectly periodical
structure. All that peak shape information is lost in the PDF...
So, both PDF and Rietveld approaches may appear necessary
and complementary, sometimes - for ill-crystallized compounds.
However, is it really necessary to see on the PDF the difference
between the Si-O and Al-O distances in respectively SiO4 and AlO4 ?
This is already a well established fact (the same for any statistical
substitution of atoms with different radii like In and Ga in (In/Ga)As).
So, this PDF advantage does not impress me a lot (like opening an
already open door), EXAFS reveals the same. Apart from being able
to show such differences, I expect more from the PDF approach, but
the more an ill-crystallized sample is close to be amorphous, and the
more the structure hypothesis will be dubious...
Armel

Re: Rietveld refinement and PDF refinement ?

[Jon Wright]

Well, that is an old chestnut that Cooper and Rollet used to oppose to
Rietveld refinement. I think Rollet eventually agreed that Rietveld was
the better method. Has Bill really gone back on that ?
 

The difference between the two approaches are just an interchange of the 
order of summations within a Rietveld program. Differences in esds 
should only arise through differences in accumulated rounding errors, 
assuming you don't apply any fudge factors. Since most people do apply 
fudge factors, the argument is really about which fudge factor you 
should apply. I will only comment that the conventional Rietveld 
approach (multiply the covariance matrix by chi^2) is often poor.

As for the PDF versus Rietveld - you should get smaller esds on 
thermal factors if you were to write a program which treats the 
background as a part of the crystal structure and has no arbitrary 
degrees of freedom in modelling the background. This is just due to 
adding in more data points that are normally treated as background but 
which should help to determine the thermal parameters via the diffuse 
scattering.

So, provided you were to remove the arbitrary background from the 
Rietveld program and compute the diffuse scattering the methods ought to 
be equivalent. Something like DIFFAX does this already for a subset of 
structures, but I think without refinement. The real difficulty arises 
with how to visualise the disordered component, decide what it is, and 
improve the fit - hence the use of the PDF. Although no one appears to 
have written such a program there does not seem to be any fundamental 
reason why it is not possible (compute the PDF to whatever Q limit you 
like, then transform the PDF and derivatives into reciprocal space). 
Biologists already manage to do this in order to use an FFT for 
refinement of large crystal structures!

In practice a large percentage of the beamtime for these experiments at 
the synchrotron is used to measure data at very high Q which visually 
has relatively little information content - just so that a Fourier 
transform can be used to get the PDF. This is silly! The model can 
always be Fourier transformed up to an arbitrary Q limit and then 
compared whatever range of data you have. For things like InGaAs the 
diffuse scatter bumps should occur mainly on the length scale of the 
actual two bond distances. Wiggles on shorter length scales  are going 
to be more and more dominated by the thermal motion of the atoms, and so 
don't really add as much to the picture (other than to allow an 
experimentalist to get some sleep!).

In effect it is like the difference between measuring single crystal 
data to the high Q limit and then computing an origin removed Patterson 
function and doing a refinement against that Patterson as raw data. No 
one does the latter as you can trivially avoid the truncation effects by 
doing the refinement in reciprocal space. The question then is whether 
it is worth using up most of your beamtime to measure the way something 
tends toward a constant value very very precisely? Could the PDF still 
be reconstructed via maximum entropy techniques from a restricted range 
of data for help in designing the model? Currently the PDF approach 
beats crystallographic refinement by modelling the diffuse scattering. 
As soon as there is a Rietveld program which can model this too then one 
might expect the these experiments become more straightforward away from 
the ToF source.

I'd be grateful if someone can correct me and show that most of the 
information is at the very high Q values. Visually these data contain 
very little compared to the oscillations at lower Q and seem to become 
progressively less interesting the further you go, as there is a larger 
and larger random component due to thermal motion. Measuring this just 
so you can do one transform of the data instead of transforms of the 
computed PDF and derivatives seems like a dubious use of resources? 
Since the ToF instruments get this data whether they like it or not, the 
one transform approach is entirely sensible there. For x-rays and CW 
neutrons, it seems there is a Rietveld program out there waiting to be 
modified.

August is still with us, Happy Silly Season!
Jon

RE: Rietveld refinement and PDF refinement ?

[Radaelli, PG (Paolo)]

 I would argue that the Bragg 
 diffuse scattering both reflect the average instantaneous atomic
 structure.

Yes. If you integrate over energy, the scattering function factors to a
delta function in time, corresponding to an instantaneous snapshot of the
spatial correlations. It is not a question of Bragg or or diffuse
scattering.

Your statement about integrating over energy is correct regardless of Bragg
or diffuse scattering, but Brian's statement is not, at least in the context
of the PDF/Bragg discussion, so it is and it isn't would have been a more
appropriate statement on my part.

It is true that in diffraction you measure the intermediate scattering
function S(Q,t=0), but this is not the same thing as saying that you can
then Fourier-transform any part of it you like to a G(x, t=0).  To get a
real-space function G(x) you have to integrate over the *whole* Q domain,
and in doing so for Bragg scattering you set to zero everything that is
outside the nodes of the RL.  However, it is easy to see that this can be
equivalent to setting an energy cut-off.  This is because fluctuations in
time and space are usually correlated, so by selecting an integration range
in Q for you Bragg peaks, you also effectively select an integration range
in energy.  Your superstructure example shows it clearly:  if you are far
from the phase transition and the correlation length of your tilt
fluctuation is 10 A,  you would not see a Bragg peak there and you would get
the time-average structure (without the superstructure).  Clearly there is
the limiting case of critical scattering very near the phase transition,
where the fluctuating regions are so large that you effectively take a
snapshot of each of them.  There could even be a deeper point here to do
with ergodicity, whereby you could show that coherent space average and
coherent time average are effectively the same (I am not positive about
this, though). 

The point I was trying to make is a different one. We are discussing about
the difference between Bragg and PDF.  If all the scattering is near the
Bragg peaks, so that you integrate it all in crystallography, there is and
there cannot be any difference between the two techniques.  I am sure we are
not discussing this case.  The interesting case is when there is additional
diffuse scattering. What I am saying is that if this diffuse scattering is
inelastic, then PDF will reflect istantaneous correlations in a way that is
missed by Bragg scattering. Let's look at the case of two bonded atoms
again, with a bond length L, and lets this time assume that they vibrate
harmonically in the transverse  direction, and that the semi-axis of the
thermal ellipsoid is a.  The possible istantaneous bond lengths range from L
to sqrt(L^2+4a^2) for an uncorrelated or anti-correlated motion, but is
always L for a correlated motion.  Bragg scattering will give you a distance
of L between the two centres, which is only correct for correlated motion.
It also provides information about the two ellipsoids, which is the same you
would get by averaging the scattering density over time, regardless of
correlations.  Istantaneous correlations are only contained in the diffuse
scattering, and are in principle accessible by PDF.

Paolo Radaelli

Re: Rietveld refinement and PDF refinement ?

[Von Dreele, Robert B.]

Jon  others,
Well, there is an attempt at this in GSAS - the diffuse scattering functions for 
fitting these contributions separate from  the background functions. These things 
have three forms related to the Debye equations formulated for glasses. The possibly 
neat thing about them is that they separate the diffuse scattering component from the 
Bragg component unlike PDF analysis. As a test of them I can fit neutron TOF 
diffraction data from fused silica quite nicely. I'm sure others have tried them - 
we all might want to hear about their experience.
Bob Von Dreele



From: Jon Wright [mailto:[EMAIL PROTECTED]
Sent: Sun 8/22/2004 6:13 AM
To: [EMAIL PROTECTED]




Well, that is an old chestnut that Cooper and Rollet used to oppose to
Rietveld refinement. I think Rollet eventually agreed that Rietveld was
the better method. Has Bill really gone back on that ?
 

The difference between the two approaches are just an interchange of the
order of summations within a Rietveld program. Differences in esds
should only arise through differences in accumulated rounding errors,
assuming you don't apply any fudge factors. Since most people do apply
fudge factors, the argument is really about which fudge factor you
should apply. I will only comment that the conventional Rietveld
approach (multiply the covariance matrix by chi^2) is often poor.

As for the PDF versus Rietveld - you should get smaller esds on
thermal factors if you were to write a program which treats the
background as a part of the crystal structure and has no arbitrary
degrees of freedom in modelling the background. This is just due to
adding in more data points that are normally treated as background but
which should help to determine the thermal parameters via the diffuse
scattering.

So, provided you were to remove the arbitrary background from the
Rietveld program and compute the diffuse scattering the methods ought to
be equivalent. Something like DIFFAX does this already for a subset of
structures, but I think without refinement. The real difficulty arises
with how to visualise the disordered component, decide what it is, and
improve the fit - hence the use of the PDF. Although no one appears to
have written such a program there does not seem to be any fundamental
reason why it is not possible (compute the PDF to whatever Q limit you
like, then transform the PDF and derivatives into reciprocal space).
Biologists already manage to do this in order to use an FFT for
refinement of large crystal structures!

In practice a large percentage of the beamtime for these experiments at
the synchrotron is used to measure data at very high Q which visually
has relatively little information content - just so that a Fourier
transform can be used to get the PDF. This is silly! The model can
always be Fourier transformed up to an arbitrary Q limit and then
compared whatever range of data you have. For things like InGaAs the
diffuse scatter bumps should occur mainly on the length scale of the
actual two bond distances. Wiggles on shorter length scales  are going
to be more and more dominated by the thermal motion of the atoms, and so
don't really add as much to the picture (other than to allow an
experimentalist to get some sleep!).

In effect it is like the difference between measuring single crystal
data to the high Q limit and then computing an origin removed Patterson
function and doing a refinement against that Patterson as raw data. No
one does the latter as you can trivially avoid the truncation effects by
doing the refinement in reciprocal space. The question then is whether
it is worth using up most of your beamtime to measure the way something
tends toward a constant value very very precisely? Could the PDF still
be reconstructed via maximum entropy techniques from a restricted range
of data for help in designing the model? Currently the PDF approach
beats crystallographic refinement by modelling the diffuse scattering.
As soon as there is a Rietveld program which can model this too then one
might expect the these experiments become more straightforward away from
the ToF source.

I'd be grateful if someone can correct me and show that most of the
information is at the very high Q values. Visually these data contain
very little compared to the oscillations at lower Q and seem to become
progressively less interesting the further you go, as there is a larger
and larger random component due to thermal motion. Measuring this just
so you can do one transform of the data instead of transforms of the
computed PDF and derivatives seems like a dubious use of resources?
Since the ToF instruments get this data whether they like it or not, the
one transform approach is entirely sensible there. For x-rays and CW
neutrons, it seems there is a Rietveld program out there waiting to be
modified.

August is still with us, Happy Silly Season!

Jon

RE: Rietveld refinement and PDF refinement ?

[Radaelli, PG (Paolo)]

Two very good points by Armel:

all the very good PDF studies ...are made by using synchrotron data or
neutron data from spallation
sources

This is because they are the only means to get to high Q (i.e., high
resolution in real space) and sufficiently high resolution (in reciprocal
space) simultaneously.  The RMC method is somewhat similar and does not
require such high Q, but it has the drawback of requiring a starting model
(arguably, there is also a uniqueness issue with RMC).  One nice feature of
the latest generation of TOF instruments is that one does not have to choose
in advance between PDF and crystallography, as long as one has appropriate
references (empty can, empty instrument etc.), which are collected as a
matter of course anyway.  PDF analysis requires better statistics, but, in
the context of a large phase diagram study, it is always possible to collect
a few data point to PDF accuracy.

So, this PDF advantage does not impress me a lot

True, in most cases PDF=Rietveld + Common Sense.  However, there are some
exceptions.  For some nice cases see the work of Simon Hibble et al. (e.g.,
Hibble SJ, Hannon AC, Cheyne SM Structure of AuCN determined from total
neutron diffraction INORG CHEM 42 (15): 4724-4730 JUL 28 2003 and references
cited therein) and that by Simon Billinge (e.g. Petkov V, Billinge SJL,
Larson P, et al.
Structure of nanocrystalline materials using atomic pair distribution
function analysis: Study of LiMoS2 PHYS REV B 65 (9): art. no. 092105 MAR 1
2002 ).  Particularly, Simon Billinge makes the point that the future of PDF
is in the study of materials with short and intermediate-range order but no
long-range order (nano-crystallography).  It is an interesting point of
view, although, at the moment, there are not very many examples of this in
the literature.

Paolo Radaelli

RE: Rietveld refinement and PDF refinement ?

[Hewat Alan]

 Two very good points by Armel:
all the very good PDF studies ...are made by using synchrotron data or
neutron data from spallation sources

And he is modest as well :-) But do you really have the resolution even on
HRPD to see the diffuse scattering between Bragg peaks at high Q ? You may
get better temperature factors with high-Q PDF refinement, but you will
also do that with high-Q Rietveld.

I also doubt that just because PDF uses data between the Bragg peaks, then
it must be superior for seeing details not centered on atoms in real space
in a crystal, eg the split atom sites in (In/Ga)As). You might do just as
well with Bragg scattering if you use the result of Rietveld refinement to
construct a Fourier map of the structure. Happily, a sampling of
reciprocal space (Bragg peaks) is sufficient to re-construct the entire
density of a periodic structure in real space, not just point atoms, to a
resolution limited only by Q.

 What I am saying is that if this
 diffuse scattering is inelastic, then PDF will reflect istantaneous
 correlations in a way that is missed by Bragg scattering.

But you do agree that in a PDF experiment you integrate over energy, so
you only see an instantaneous snapshot of the structure, ie the spatial
correlations. If it is a periodic structure, you also average over unit
cells, even though the spatial correlations are different from one cell to
the next. (BTW, talk of inelastic scattering raises the question of
different inelastic cross-sections for the very different neutron energies
used on your TOF machine).

So while I am convinced of the interest of PDF for non-crystalline
materials, with short or intermediate range order, I am not yet convinced
that you gain much from PDF refinement of crystalline materials, where you
can also apply Rietveld refinement. A Rietveld refinement probably has
fewer correlations between parameters, and can be used to construct a
Fourier map of the complete scattering density, while PDF is only a
Patterson map of the pair correlations, and a lot more difficult to
interpret.

Alan.

Re: Rietveld refinement and PDF refinement ?

[Von Dreele, Robert B.]

I'd only add that given the clue that the peak in GaInAs is split from the PDF then 
one should model it that way in a Rietveld refinement. It should agree. The thrown 
away info in a Rietveld refinement is also evident in the Bragg peak intensities - 
shows up as funny thermal parameters, low atom fractions, odd bond lengths, etc. in 
the results. I should also say that it isn't fair to compare truncated (in Q) Rietveld 
refinements with untruncated PDF refinements  say the latter is better. Let's be 
even-steven about this.



From: Alan Hewat [mailto:[EMAIL PROTECTED]
Sent: Thu 8/19/2004 9:31 AM
To: [EMAIL PROTECTED]
Cc: [EMAIL PROTECTED]




But if you refine the full data with the same model, can there really be any 
fundamental difference, if in one case you simply do a Fourier transform to real 
space ?

Thanks to Stefan Bruehne for providing an obvious (in retrospect :-) answer i.e. that 
in Rietveld refinement we throw away the non-Bragg peak data, where-as with PDF all 
scattering is included.

He quoted an example where PDF shows a split peak in Ga(1-x)In(x)As for Ga-As and 
In-As distances, where Rietveld refinement always gives the average (Ga,In)As 
structure.

Alan.

Alan Hewat, ILL Grenoble, FRANCE  [EMAIL PROTECTED] fax (33) 4.76.20.76.48
(33) 4.76.20.72.13 (.26 Mme Guillermet) http://www.ill.fr/dif/AlanHewat.htm
___

RE: Rietveld refinement and PDF refinement ?

[Radaelli, PG (Paolo)]

The only truly unique PDF information is about *correlations*.  Let's say
you have two bonded sites, both with anisotropic thermal ellipsoids along
the bond, and let's assume that the motion is purely harmonic.  A sharp PDF
peak will indicate that the atoms move predominanly in-phase, a broad PDF
peak that the atoms move predominantly out-of-phase.  The two scenarios will
give identical Fourier maps as reconstructed from the Bragg peaks, whatever
the Qmax, so the additional width (or additional narrowness) of the peak
with respect to an uncorrelated model arises purely from the non-Bragg
scattering.  You can make the same argument for static correlations.
Ga(1-x)In(x)As is a typical case.  It is not a split-site problem, in that
both Ga/In and As will be slightly displaced locally depending on their
surrounding, but the displacements are correlated in such a way as to give a
shorter bond length for Ga-As and a longer one for In-As.
Of course, PDF is also used to look at more general issues of static/dynamic
disorder that could also be examined using Bragg scattering, and in many
case it does quite well.  PDF is not (yet) very good for structural
refinements (so it is to be used only in desperate cases of highly
disordered systems) and is pretty hopeless for weak ordered displacement
patters, since the extra Bragg peaks in crystallography lock-in on the new
modulation even in the presence of large unrelated displacements.   For this
very reason, PDF tends to miss phase transitions, particularly at higher
temperatures, which led to some very wierd claims in the past literature.
There is a lot of controversy about PDF being able to say something about
weak disordered displacement patters (e.g., dynamic stripes), but I am
personally very skeptical.  PDF requires exquisite data and a true passion
for data analysis.  If you have a good problem, you can get (probably) the
best PDF data worldwide almost routinely on my instrument GEM at the ISIS
facility (see also the cited paper by Billinge).

Paolo Radaelli