Re: Misconduct

[Kurt Leinenweber]

Hi, in our work we still sometimes encounter entirely new compounds with simple 
structures like rocksalt, spinel, etc.  in order to convince ourselves and our 
readers that the materials are real, we have to fit the powder patterns - put 
in the atoms, refine lattice parameter(s), show that thermal parameters are 
reasonable, fit the peak shapes, background etc all together.  In the case of 
spinels for example we can also refine the single atomic parameter and show 
that the bond lengths are reasonable.  The refinements are used to decide 
whether sites are fully occupied and to decide the valence of the cation when 
multiple valence states are possible.  It’s not the kind of thing that would 
get people really excited with the crystallographic methods, but it is 
necessary for convincing ourselves and others that the identification of the 
compound is reasonable.  Is that Rietveld refinement?  I don’t know so I call 
upon the list to say.

Kurt

Get Outlook for iOS

From: rietveld_l-requ...@ill.fr  on behalf of 
Matthew Rowles 
Sent: Sunday, January 14, 2024 11:04:25 PM
To: Alan W Hewat 
Cc: Le Bail Armel ; Rietveld_L 
Subject: Re: Misconduct

I see the core contribution of the Rietveld method as the point-wise 
calculation of a powder pattern. This then enables the refinement of the 
parameters.

Yes, attributing QPA to Rietveld is incorrect; that is mainly due to 
Hill/Howard and Bish/Howard - I try to make it a point to differentiate this.

calling PDF refinements Rietveld refinements is just plain wrong (afaik), 
unless you actually are moving crystallographic parameters around, in which 
case, the nomenclature gets fuzzy..

On Sat, 13 Jan 2024 at 14:39, Alan W Hewat 
mailto:alan.he...@neutronoptics.com>> wrote:
The core of Rietveld refinement is REFINING the crystallographic parameters to 
fit the pattern. That was the great innovation. Is that done here ? To 
calculate various patterns to refine phase composition you necessarily need 
models of the crystal structures. But all refinements of powder patterns are 
not Rietveld Refinement. Quantitative analysis of powder samples is an 
important technique, and to attribute that to Rietveld is wrong. Same goes for 
Pair Distribution Function analysis. Calling everything "Rietveld Refinement" 
is not helpful, and actually hides the fundamental contribution of this 
technique to crystallography.


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


On Sat, 13 Jan 2024, 07:00 Matthew Rowles, 
mailto:rowle...@gmail.com>> wrote:
Hard disagree here.

You're using crystallographic parameters to calculate the (intensities and 
positions of the) pattern.

To me, that's the core of Rietveld refinement.

You need to apply a peak shape model. Why not apply a model from which you can 
extract crystallite parameters?

QPA can then be done on the output of a refinement, eg application of the 
internal standard method using the Hill /Howard algorithm.

Its still a Rietveld refinement, I'm not just fitting peaks willy nilly; 
they're constrained by a crystal model.


Matthew

On Sat, 13 Jan 2024, 01:48 Alan W Hewat, 
mailto:alan.he...@neutronoptics.com>> wrote:
Apart from the record number of atoms, phases, parameters, citations etc used 
to describe just 3 broad peaks, I object to this kind of refinement being 
called "Rietveld refinement". Luca called it "Rietveld-like" in MAUD, which was 
used here, but even that is wrong. The term "Rietveld refinement" should be 
restricted to the refinement of crystallographic parameters - cell dimensions, 
atom coordinates etc. and not applied to quantitative analysis of phases, 
particle size etc. Fitting peaks in powder patterns was done before Rietveld, 
who must be turning in his grave to see his name associated with this kind of 
thing.


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


On Fri, 12 Jan 2024, 12:57 Le Bail Armel, 
mailto:le-bail.ar...@orange.fr>> wrote:

Hi,

A good candidate for the "worst Rietveld refinement of the year" award :

https://pubpeer.com/publications/12069A6AD9D5D34F26031F34705D06

Even the difference pattern is tot

RE: [EXT] Re: [External] Re: Step-like basline

[Kurt Leinenweber]

Hi,  Are these things modeled in Rietveld programs, by chance?  It seems like a 
lot of baggage to put in a refinement but if it makes the results better...


  *   Kurt

From: rietveld_l-requ...@ill.fr  On Behalf Of Thomas 
Gegan
Sent: Sunday, September 3, 2023 9:16 AM
To: Bish, David L ; Shay Tirosh ; 
Fernando Igoa 
Cc: Rietveld List (rietveld_l@ill.fr) 
Subject: RE: [EXT] Re: [External] Re: Step-like basline

I agree with a Ni absorption edge, possibly with a Kβ peak around 38° 2θ.

Tom Gegan
Chemist III

Phone: +1 732 205-5111, Email: tom.ge...@basf.com
Postal Address: BASF Corporation, , 25 Middlesex Essex Turnpike, 08830 Iselin, 
United States
[cid:image001.png@01D9DE4C.79FBB4C0]

From: rietveld_l-requ...@ill.fr 
mailto:rietveld_l-requ...@ill.fr>> On Behalf Of 
Bish, David L
Sent: Sunday, September 3, 2023 7:08 AM
To: Shay Tirosh mailto:stiro...@gmail.com>>; Fernando Igoa 
mailto:fer.igoa.1...@gmail.com>>
Cc: Rietveld List (rietveld_l@ill.fr) 
mailto:rietveld_l@ill.fr>>
Subject: [EXT] Re: [External] Re: Step-like basline

Some people who received this message don't often get email from 
b...@indiana.edu. Learn why this is 
important
Hello Shay,
I think it is probably related to "tube tails". You can read about this in the 
literature (e.g., on the BGMN web site) and you can model it in some Rietveld 
software such as Topas. You don't normally notice this but it becomes apparent 
with higher-intensity peaks.

Regards,
Dave

From: rietveld_l-requ...@ill.fr 
mailto:rietveld_l-requ...@ill.fr>> on behalf of 
Fernando Igoa mailto:fer.igoa.1...@gmail.com>>
Sent: Sunday, September 3, 2023 3:06 AM
To: Shay Tirosh mailto:stiro...@gmail.com>>
Cc: Rietveld List (rietveld_l@ill.fr) 
mailto:rietveld_l@ill.fr>>
Subject: [External] Re: Step-like basline

This message was sent from a non-IU address. Please exercise caution when 
clicking links or opening attachments from external sources.

Hey Shay,

Are you using a motorized slit during the measurement? These may open up 
abruptly to compensate for the angular dependence of the footprint and thus 
generate an abrupt increase in the intensity.

Hope it helps :)

On Sun, Sep 3, 2023, 8:50 AM Shay Tirosh 
mailto:stiro...@gmail.com>> wrote:
Dear Rietvelders
I am attaching a zoom-in on a diffraction profile.
My question is what is the origin of the step-like profile next to a very large 
reflection peak?
Is it a sample preparation problem?
Is it part of the baseline?
[cid:image003.png@01D9DE4C.79FBB4C0]
Thanks
Shay
--









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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: Obtaining a silicon standard wafer

[Kurt Leinenweber]

I for one, don’t blame Jim for wanting this plot to appear in an official 
publication rather than as a “freebie” on a web site.  He will get more credit 
for it this way.


-  Kurt

From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On Behalf Of 
Cline, James Dr.
Sent: Tuesday, July 14, 2015 9:59 AM
To: Alan Hewat
Cc: rietveld_l@ill.fr
Subject: RE: Obtaining a silicon standard wafer

Hi,
Why don't you put these plots on your sales site...
The SRM people would never do this as they would have to explain the plot in a 
technical manner to inquiring customers.
Well, the documents on the NIST site are already quite technical, and contain 
plots, just not the nice comparative plots  you might need when choosing a line 
standard eg 
https://www-s.nist.gov/srmors/certificates/view_certGIF.cfm?certificate=640E


I did, indeed, include this plot (and a discussion of it) in the Vol H paper 
and have taken measures to get it available online sooner, rather than later.

Jim


James P. Cline
Materials Measurement Science 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

From: alan.he...@gmail.com 
[mailto:alan.he...@gmail.com] On Behalf Of Alan Hewat
Sent: Tuesday, July 14, 2015 12:20 PM
To: rietveld_l@ill.fr
Subject: Re: Obtaining a silicon standard wafer

if you would like a preprint, send me an email.

Yes, that's the way people should offer supplementary material to list users. 
Or even better, link to your preprint.

Why don't you put these plots on your sales site...
The SRM people would never do this as they would have to explain the plot in a 
technical manner to inquiring customers.

Well, the documents on the NIST site are already quite technical, and contain 
plots, just not the nice comparative plots  you might need when choosing a line 
standard eg 
https://www-s.nist.gov/srmors/certificates/view_certGIF.cfm?certificate=640E

> What year is it ? I find it silly to discuss inclusion of a 64K image in email

OK Frank, but until someone sets up an email archive that reproduces images, 
they are lost to others if they are simply included in an email - see 
https://www.mail-archive.com/faq.html#attachments and the bit about performance.

Frankly, I am indeed a little old-fashioned. If you can't find it with 
Google... it doesn't exist.

Alan.
__
   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: What's in a name?

[Kurt Leinenweber]

Hi all,



The question could be very Rietveld-related if the person wants to know how 
well the D2 Phases diffractometer works in getting Ritveld-refinable data.  
Sometimes companies want to sell new types of focusing optics etc. and it is 
very relevant to find out whether such optics might make Rietveld refinement 
difficult.



- Kurt




From: alan.he...@gmail.com [alan.he...@gmail.com] on behalf of Alan Hewat 
[alan.he...@neutronoptics.com]
Sent: Friday, July 03, 2015 10:03 AM
To: Timothy Hyde
Cc: rietveld_l@ill.fr
Subject: Re: What's in a name?

No problem with people asking "not strictly Rietveld" questions Tim.
But the list is named in honour of Hugo Rietveld, and that seems right to me.
Besides, it's shorter than either of your suggested titles :-)
Alan.

On 3 July 2015 at 18:35, Timothy Hyde 
mailto:timothy.h...@matthey.com>> wrote:
“Dear All,
Sorry not a direct Rietveld question, but I hope somebody can help……….”

Alan,

Second such question of the day! Perhaps (not wanting to go too much over old 
ground re Facebook/social media etc) all that is required to grow 
membership/usage is a simple name change of the group? I suggest “Sorry not a 
direct Rietveld question, but I hope somebody can help…”

Perhaps  “XRD and Rietveld” would be less cumbersome and inform potential new 
members that Rietveld is only a fraction of the discussion topics on the list? 
Any thoughts?

Tim Hyde


From: rietveld_l-requ...@ill.fr 
[mailto:rietveld_l-requ...@ill.fr] On Behalf 
Of Natale Perchiazzi
Sent: 03 July 2015 16:10
Cc: rietveld_l@ill.fr
Subject: D2 phaser info





Dear All,
Sorry not a direct Rietveld question, but I hope somebody can help. We are 
evaluating to get a D2 Phaser diffractometer. If somebody has got this 
equipment and wish to share his experience with the machine, infos are warmly 
welcome .
Best regards Natale Perchiazzi
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--
__
   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE
 +33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
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++

RE: Apologies... The "No Attachment" rule.

[Kurt Leinenweber]

Hi Darren,

That’s a very good point and clarification.


-  Kurt

From: Darren Broom [mailto:darrenbr...@inbox.com]
Sent: Sunday, May 10, 2015 6:54 AM
To: rietveld_l@ill.fr
Cc: Kurt Leinenweber
Subject: RE: Apologies... The "No Attachment" rule.

Hi Kurt

Maybe I should let others comment first but I would just like to say that I 
think a slightly harsh comment to an experienced person who has made a silly 
mistake is quite different to an abrupt and perhaps patronizing comment to a 
complete beginner who has asked a legitimate question.

I have checked back and it was definitely the latter that Bill Reese was 
commenting on previously...

Cheers,

Darren
-Original Message-
From: ku...@asu.edu<mailto:ku...@asu.edu>
Sent: Sun, 10 May 2015 13:26:28 +
To: rietveld_l@ill.fr<mailto:rietveld_l@ill.fr>
Subject: RE: Apologies... The "No Attachment" rule.

Hi,



The subject of snarky comments is a fascinating one.  I have definitely been 
the recipient of snarky comments for some of my more stupid posts on this list. 
 The good thing about them is that it lets you know that you are saying or 
doing something, crystallographically speaking, that is really unpalatable to 
someone out there, and you might need to know this for your own good.  I have 
definitely been chastised and have learned some things over the years by being 
forced to read a snarky response to one of my posts.  But on the other hand, to 
a beginner a snarky comment can be damaging.  However, these comments are not 
confined to mailing lists – they happen at conferences too and they are just 
part of the fabric of science.  As long as the whole list does not descend into 
a chaos of snarky comments, I think it’s OK to let them get through.  One 
possible remedy is for others to come to the defence of a victim of excessive 
snarkiness.  I have seen that happen on this list sometimes, and other times 
have been tempted myself to intervene, though I usually have not been brave 
enough (especially when the snark source is someone famous).



-  Kurt



From: rietveld_l-requ...@ill.fr<mailto:rietveld_l-requ...@ill.fr> 
[mailto:rietveld_l-requ...@ill.fr] On Behalf Of Darren Broom
Sent: Sunday, May 10, 2015 3:36 AM
To: Alan Hewat; Leopoldo Suescun
Cc: rietveld_l@ill.fr<mailto:rietveld_l@ill.fr>
Subject: RE: Apologies... The "No Attachment" rule.



Hi Alan

Thanks for the explanation. The point about the archive seems to me to be the 
most persuasive - I see what you mean. Providing the file sharing links stay 
active that does ensure the archive remains useful without having to "host" 
additional files on the archive server.

It does seem that removing any attachments automatically would be the best 
solution. Hopefully Song Zhen's suggestion will help sort that out.

Incidentally, Jon nicely illustrated one of the things about the list that I 
really appreciate, by posting an interesting link that I hadn't seen before and 
probably wouldn't have come across otherwise.

Also, I wondered if you could set up SYMPA so that it strips emails of any 
unnecessary snarkiness (above a predefined threshold)?

Best regards,

Darren



-Original Message-
From: alan.he...@neutronoptics.com<mailto:alan.he...@neutronoptics.com>
Sent: Sat, 9 May 2015 11:39:46 +0200
To: leopo...@fq.edu.uy<mailto:leopo...@fq.edu.uy>
Subject: Apologies... The "No Attachment" rule.

Dear Rietveld list.



Good to see so many people asking for the list to be continued. And even an 
example of an interesting scientific question immediately answered by an 
expert. Encouraging.



So why do I forbid "sinful" attachments ? (No, it's not because I'm getting old 
and snarky, though we all do eventually :-) Think of the Rietveld list as a 
kind of relaxed "Twitter", except that you are not limited to 140 characters. 
And what about Google's decision this month to favour sites that can be used on 
a mobile phone ? Yes, even oldies use mobile phones for email. SMS is another 
example of beauty in brevity.



Then the Rietveld Archive is an excellent record of past discussions - without 
the attachments. Messages that rely on attachments are then often 
incomprehensible - look up that message on 
https://www.mail-archive.com/rietveld_l@ill.fr/ Frankly, if you need more than 
that, put it on a webserver with a link to it. Such links are preserved in the 
archive.



If you see my own warning about "no attachments" as an attachment :-) perhaps 
you should check how your email client is set up. Or tell me how I can do it 
differently with SYMPA www.sympa.org<http://www.sympa.org> I didn't design the 
mail server nor the mail archive. Clearly, it is difficult to enforce a simple 
"no attachments" rule, so what would it be like policing a "small attachments" 
rule ? Even if you personally ha

RE: Apologies... The "No Attachment" rule.

[Kurt Leinenweber]

Hi,

The subject of snarky comments is a fascinating one.  I have definitely been 
the recipient of snarky comments for some of my more stupid posts on this list. 
 The good thing about them is that it lets you know that you are saying or 
doing something, crystallographically speaking, that is really unpalatable to 
someone out there, and you might need to know this for your own good.  I have 
definitely been chastised and have learned some things over the years by being 
forced to read a snarky response to one of my posts.  But on the other hand, to 
a beginner a snarky comment can be damaging.  However, these comments are not 
confined to mailing lists - they happen at conferences too and they are just 
part of the fabric of science.  As long as the whole list does not descend into 
a chaos of snarky comments, I think it's OK to let them get through.  One 
possible remedy is for others to come to the defence of a victim of excessive 
snarkiness.  I have seen that happen on this list sometimes, and other times 
have been tempted myself to intervene, though I usually have not been brave 
enough (especially when the snark source is someone famous).


-  Kurt

From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On Behalf Of 
Darren Broom
Sent: Sunday, May 10, 2015 3:36 AM
To: Alan Hewat; Leopoldo Suescun
Cc: rietveld_l@ill.fr
Subject: RE: Apologies... The "No Attachment" rule.

Hi Alan

Thanks for the explanation. The point about the archive seems to me to be the 
most persuasive - I see what you mean. Providing the file sharing links stay 
active that does ensure the archive remains useful without having to "host" 
additional files on the archive server.

It does seem that removing any attachments automatically would be the best 
solution. Hopefully Song Zhen's suggestion will help sort that out.

Incidentally, Jon nicely illustrated one of the things about the list that I 
really appreciate, by posting an interesting link that I hadn't seen before and 
probably wouldn't have come across otherwise.

Also, I wondered if you could set up SYMPA so that it strips emails of any 
unnecessary snarkiness (above a predefined threshold)?

Best regards,

Darren

-Original Message-
From: alan.he...@neutronoptics.com
Sent: Sat, 9 May 2015 11:39:46 +0200
To: leopo...@fq.edu.uy
Subject: Apologies... The "No Attachment" rule.
Dear Rietveld list.

Good to see so many people asking for the list to be continued. And even an 
example of an interesting scientific question immediately answered by an 
expert. Encouraging.

So why do I forbid "sinful" attachments ? (No, it's not because I'm getting old 
and snarky, though we all do eventually :-) Think of the Rietveld list as a 
kind of relaxed "Twitter", except that you are not limited to 140 characters. 
And what about Google's decision this month to favour sites that can be used on 
a mobile phone ? Yes, even oldies use mobile phones for email. SMS is another 
example of beauty in brevity.

Then the Rietveld Archive is an excellent record of past discussions - without 
the attachments. Messages that rely on attachments are then often 
incomprehensible - look up that message on 
https://www.mail-archive.com/rietveld_l@ill.fr/ Frankly, if you need more than 
that, put it on a webserver with a link to it. Such links are preserved in the 
archive.

If you see my own warning about "no attachments" as an attachment :-) perhaps 
you should check how your email client is set up. Or tell me how I can do it 
differently with SYMPA www.sympa.org I didn't design the 
mail server nor the mail archive. Clearly, it is difficult to enforce a simple 
"no attachments" rule, so what would it be like policing a "small attachments" 
rule ? Even if you personally have lots of space for email, our webserver (for 
which we don't pay) would still have to distribute ~1500 copies of your "small 
attachment".

In this particular case, a figure from an unpublished paper was published and 
criticised out of context. Is that really fair? If it's from a referee's copy 
we shouldn't even refer to it, let alone publish it. If it's a pre-print, just 
publish a link to it. But there are already plenty of examples in the published 
literature if you are looking for evidence of regression.

So where are the "Apologies"? There are none :-) "Excuse me" is what people say 
when they elbow their way through a crowd. (I only do that when I really need 
to). So if you really need to attach a document, go ahead. After all, you can 
still read the list on the archive.

Alan
__
   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE
mailto:alan.he...@neutronoptics.com>> 
+33.476.98.41.68
http://www.NeutronOptics.com/hewat
__
++
Please do NOT attach files to the

RE: regress in crystallographic good practices and knowledge

[Kurt Leinenweber]

P.S.  When the splitting arises from a phase transition, sometimes we see what 
we call "snowmen" or pairs of spots that are split between the two rings.  I 
interpret these as twins arising from the phase transition.  Has anyone seen 
these types of pairs of spots before?  I think there is a lot of information 
there that we are passing up if we don't learn to interpret it.

>Hi all,

>In my defense, 10 of the 12 messages relating to this topic have had their 
>footers attached.  I will try to figure out how to get rid of it for next time.

>Here is a topic I am interested in: we are collecting a lot of data on an 
>imaging plate (GSECARS and HPCAT at Advanced Photon Source).  We are 
>interested in splitting of peaks in some of the samples.  The splitting is 
>very difficult to see on the integrated pattern, but very easy to see on the 
>2-D imaging plate frame itself.  The rings are "spotty" and it's very easy to 
>tell which spots are in which ring when the peak is slightly split.

>My question is whether there is software I can use to take advantage of this 
>and fit the "spots" so I can get a better resolution of the splitting.  
>Something in between powder and single crystal.

>Thank you,

>- Kurt
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++

RE: regress in crystallographic good practices and knowledge

[Kurt Leinenweber]

Hi all,

In my defense, 10 of the 12 messages relating to this topic have had their 
footers attached.  I will try to figure out how to get rid of it for next time.

Here is a topic I am interested in: we are collecting a lot of data on an 
imaging plate (GSECARS and HPCAT at Advanced Photon Source).  We are interested 
in splitting of peaks in some of the samples.  The splitting is very difficult 
to see on the integrated pattern, but very easy to see on the 2-D imaging plate 
frame itself.  The rings are "spotty" and it's very easy to tell which spots 
are in which ring when the peak is slightly split.

My question is whether there is software I can use to take advantage of this 
and fit the "spots" so I can get a better resolution of the splitting.  
Something in between powder and single crystal.

Thank you,

- Kurt

-Original Message-
From: Larry Finger [mailto:larry.fin...@gmail.com] On Behalf Of Larry Finger
Sent: Friday, May 08, 2015 9:58 AM
To: Kurt Leinenweber; Alan Hewat; Leopoldo Suescun
Cc: rietveld_l@ill.fr
Subject: Re: regress in crystallographic good practices and knowledge

On 05/08/2015 11:16 AM, Kurt Leinenweber wrote:
> Hi Alan,
>
> I still like the Rietveld list and do read all the posts.
>
> Is it possible to block attachments so that people can’t attach files any 
> more?
>
> -Kurt

Thus writes the guy whose mailer blindly attaches a message footer rather than 
in-lining a signature. :)

Although I no longer practice crystallography, and no longer read the 
literature, I do find the discussions here of interest. At least I can follow 
how little crystallography the average solid-state researcher actually knows. 
Sad to know that bugs in a few programs could completely derail the science. 
All the greats of the early part of the 20th century must be really spinning in 
their graves!

Larry

++
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++

RE: regress in crystallographic good practices and knowledge

[Kurt Leinenweber]

Hi Alan,

I still like the Rietveld list and do read all the posts.

Is it possible to block attachments so that people can’t attach files any more?


-  Kurt

From: alan.he...@gmail.com [mailto:alan.he...@gmail.com] On Behalf Of Alan Hewat
Sent: Friday, May 08, 2015 9:07 AM
To: Leopoldo Suescun
Cc: rietveld_l@ill.fr
Subject: Re: regress in crystallographic good practices and knowledge

I apologize in advance for attaching a file but I cannot share my astonishment 
without it.
that´s why I worry more and more every day.

And I worry that people are still attaching files to the whole list when they 
are explicitly asked not too. Most papers are on-line now, so just give a link 
to the paper. Or post your file to a free file sharing service - see: 
http://en.wikipedia.org/wiki/Comparison_of_file_hosting_services

Anyone who still posts files to the whole list is automatically suspended for 1 
week.

Actually, I worry that the Rietveld list no longer serves a useful purpose. 
There are few interesting discussions, and apparently few people actually read 
the posts.

Alan
__
   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: XRD graphene

[Kurt Leinenweber]

Please excuse my stupid post.. if it's only one layer, you won't see any Bragg 
reflection in the 00l direction.  You need multiple layers for that!  (should I 
withdraw from the group?)

- Kurt

____
From: Kurt Leinenweber
Sent: Tuesday, November 25, 2014 6:09 PM
To: Nelson Duarte; rietveld_l@ill.fr
Subject: RE: XRD graphene

I think graphene is only one layer so you should only see 00l reflections.  
It's a 2 dimensional problem.  But I have no actual experience with it (other 
than listening to people talk about it).

- Kurt


From: rietveld_l-requ...@ill.fr [rietveld_l-requ...@ill.fr] on behalf of Nelson 
Duarte [nelson.dua...@ipn.pt]
Sent: Tuesday, November 25, 2014 5:34 PM
To: rietveld_l@ill.fr
Subject: XRD graphene

Dear rietvelds

We index graphene samples with ICDD card of graphite, correct ?
Wich ICDD card of graphite are usualy used ?

Thanks in advance

Best rergards++
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++

RE: XRD graphene

[Kurt Leinenweber]

I think graphene is only one layer so you should only see 00l reflections.  
It's a 2 dimensional problem.  But I have no actual experience with it (other 
than listening to people talk about it).

- Kurt


From: rietveld_l-requ...@ill.fr [rietveld_l-requ...@ill.fr] on behalf of Nelson 
Duarte [nelson.dua...@ipn.pt]
Sent: Tuesday, November 25, 2014 5:34 PM
To: rietveld_l@ill.fr
Subject: XRD graphene

Dear rietvelds

We index graphene samples with ICDD card of graphite, correct ?
Wich ICDD card of graphite are usualy used ?

Thanks in advance

Best rergards++
Please do NOT attach files to the whole list 
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++

RE: Phase volume fraction

[Kurt Leinenweber]

Hi Apu,

It is definitely case dependent.  If you have a sample with a known (small) 
quantity of the second phase, you can do a quantitative analysis and obtain the 
phase fraction.  Then, just diminish the phase fraction until you see the point 
of disappearance.  It disappears when the largest set of peaks is not 
distinguishable mathematically from the noise.  Obviously this depends on the 
quality of the diffraction from the phase and the level of noise in that 
particular diffractometer for that sample.

On the warhorse instrument I use the most (Siemens D5000 with CuKalpha 
radiation and position-sensitive detector) the limit is usually 1% but is worse 
for iron-bearing (or otherwise fluorescent) samples and better for very nicely 
crystalline and strong scatterers with high symmetry/multiplicity such as 
rutile, just for an example.

- Kurt


From: rietveld_l-requ...@ill.fr [rietveld_l-requ...@ill.fr] on behalf of 
Suchomel, Matthew R. [sucho...@aps.anl.gov]
Sent: Thursday, May 01, 2014 1:57 PM
To: Apu Sarkar
Cc: rietveld_l@ill.fr
Subject: Re: Phase volume fraction

With the appropriate sample and high-resolution synchrotron powder diffraction 
data, you can do even better than 0.1 wt%.

Here at the APS beamline 11-BM, we've managed to perform quantitative 
refinements on a suspected very dilute ZrB2 impurity in the NIST SRM LaB6 660a 
powder sample, at a level of 0.068 wt% ZrB2.   The accuracy of this value is 
supported by complimentary XRF data showing a calibrated Zr concentration of 
617 ppm in the LaB6 sample.

These data (from J. Faber) are currently in press as proceedings from the 2013 
DXC meeting.

It would be difficult to reproduce this level of sensitivity with more 'real 
world' samples and conditions - but it shows in principle what can be achieved. 
Especially if you submit samples for the free rapid access measurement program 
here at the APS beamline 11-BM.

http://11bm.xray.aps.anl.gov/users_new.html
[please forgive the flagrant advert!]

Matthew Suchomel
Advanced Photon Source
Argonne National Laboratory




> I guess you are talking about detection limit only, not quantification limit, 
> right?
> The answer largely depends on your material (scattering power, domain size), 
> tube (sampling volume) and counting time. I have seen cases where you can 
> clearly see something below 0.1 wt% and cases where already the percent was 
> off limits.
> Matteo
>
> -
>
>  Matteo Leoni, PhD
>
>  DICAM
>  University of Trento
>  via Mesiano, 77
>  38123 Trento
>  Italy
>
>  Tel +39 0461 282416 Fax +39 0461 282672
>
>  e-mail: matteo.le...@unitn.it
> 
>
>
> -Messaggio originale-
> Da: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] Per conto di 
> Apu Sarkar
> Inviato: giovedì 1 maggio 2014 22.24
> A: rietveld_l@ill.fr
> Oggetto: Phase volume fraction
>
> Hi,
> Can any one tell me what is the minimum phase volume fraction that can be 
> detected by a laboratory X-ray diffractometer. In there any reference for 
> this.
>
> I am using the new Empyrean from PANalytical.
>
> Thanks
> Apu
>
> Department of Nuclear Engineering
> NC State University
> Raleigh, USA
> ++
> 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: Polarization factor por Ge (111) monochromator

[Kurt Leinenweber]

Hi all,



So are all readers of the Rietveld list also supposed to search the archives 
for this information?  Tell us the answer, please!

- Kurt




From: rietveld_l-requ...@ill.fr [rietveld_l-requ...@ill.fr] on behalf of Josué 
Friedrich [josue.friedr...@gmail.com]
Sent: Sunday, April 06, 2014 12:12 PM
To: Artem Babaryk
Cc: rietveld_l@ill.fr
Subject: Re: Polarization factor por Ge (111) monochromator

Thanks Artem,

Usually I search first, but today I did not. Thanks for your help

regards, Josue

From: Artem Babaryk
Sent: Sunday, April 06, 2014 8:56 PM
To: Josu Friedrich
Cc: rietveld_l@ill.fr
Subject: Re: Polarization factor por Ge (111) monochromator

Dear Josu,

Somethimes browsing the Rietveld list archive I'm strengthening myself that
there is nothing new under the sun...

So, look there:

http://www.mail-archive.com/rietveld_l%40ill.fr/msg05129.html

Best,
Artem

06.04.2014 20:11, Josu Friedrich 
>Good afternoon,
>
> Does anyone know the polarization factor for an incident beam germanium (111) 
> monochromator used in a Panalytical XPert Pro diffractometer?
>
> Many thanks,
> Josue
++
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++

RE: the error bars of lattice parameters using GSAS

[Kurt Leinenweber]

Dear Jin Peng,
 
The uncertainties for the lattice parameters (and all the other fitted 
parameters) are in the LST file (list file).  They are shown as separate 
numbers for the lattice parameters and the uncertainties, like so:
 
13.88843  13.88843   6.53524
0.000350.000350.00014
 
- Kurt



From: Peng, Jin [mailto:jpe...@tulane.edu]
Sent: Thu 2/18/2010 5:31 PM
To: rietveld_l@ill.fr
Subject: the error bars of lattice parameters using GSAS



Hi,

I am using the graphical interface of GSAS, EXPGUI, for the refinement, the 
problem is I can not find the error bars for the lattice constant a, b, c. I 
can find the error of band length and band angles under result - disagl. Where 
can I find the error bars for a, b and c?

Thank you!

Jin Peng
Department of Physics, Tulane University
New Orleans, LA, 70118

RE: Comparison of powder patterns recorded at different wavelengths

[Kurt Leinenweber]

Hi Mike,

If he plots in d then neither of the components will have the right d-spacing 
when he uses the average - but you're right that its standard procedure.

- Kurt

 
*
Kurt Leinenweber
Dept. of Chemistry and Biochemistry
Arizona State University
Tempe, AZ 85287-1604
 
phone (480)-965-8853
fax (480)-965-2747
 
***

-Original Message-
From: Michael Glazer [mailto:m.glaz...@physics.ox.ac.uk] 
Sent: Friday, January 15, 2010 9:49 AM
To: Kurt Leinenweber; Franz Werner; rietveld_l@ill.fr
Subject: RE: Comparison of powder patterns recorded at different wavelengths

Kurt
The standard method is to use a wavelength made from the weighted (2:1) average 
of the two components. So for CuKa the standard value is 1.5418 angstroms
Mike Glazer


-Original Message-
From: Kurt Leinenweber [mailto:ku...@asu.edu] 
Sent: 15 January 2010 16:46
To: Franz Werner; rietveld_l@ill.fr
Subject: RE: Comparison of powder patterns recorded at different wavelengths

HI Franz,

It seems to me that the best thing would be to use K alpha 1 wavelength (which 
is 66 percent of the total intensity) and then mentally ignore the K alpha 2 
contribution.  The other option is to strip the original data of K alpha 2, if 
your diffractometer's software has that option, but since stripping is a kind 
of data manipulation, I don't usually like doing it.

- Kurt

 
*
Kurt Leinenweber
Dept. of Chemistry and Biochemistry
Arizona State University
Tempe, AZ 85287-1604
 
phone (480)-965-8853
fax (480)-965-2747
 
***

-Original Message-
From: Franz Werner [mailto:franzwer...@gmx.at] 
Sent: Friday, January 15, 2010 6:27 AM
To: rietveld_l@ill.fr
Subject: Comparison of powder patterns recorded at different wavelengths

Hello Rietvelders

I want to compare graphically powder patterns of a phase which were recorded at 
different wavelengths. Therefore I'd like to overlay the patterns using 
d-values, calculated from their corresponding 2theta values. In the case of 
monochromatic X-rays it's trivial. But which wavelength should one use in the 
case of Kalpha1-Kalpha2 radiation (lab instrument)?

Thanks for your help.

Regards
Franz Werner

Tallinn University of Technology
Estonia
-- 
GRATIS für alle GMX-Mitglieder: Die maxdome Movie-FLAT!
Jetzt freischalten unter http://portal.gmx.net/de/go/maxdome01

RE: Comparison of powder patterns recorded at different wavelengths

[Kurt Leinenweber]

HI Franz,

It seems to me that the best thing would be to use K alpha 1 wavelength (which 
is 66 percent of the total intensity) and then mentally ignore the K alpha 2 
contribution.  The other option is to strip the original data of K alpha 2, if 
your diffractometer's software has that option, but since stripping is a kind 
of data manipulation, I don't usually like doing it.

- Kurt

 
*
Kurt Leinenweber
Dept. of Chemistry and Biochemistry
Arizona State University
Tempe, AZ 85287-1604
 
phone (480)-965-8853
fax (480)-965-2747
 
***

-Original Message-
From: Franz Werner [mailto:franzwer...@gmx.at] 
Sent: Friday, January 15, 2010 6:27 AM
To: rietveld_l@ill.fr
Subject: Comparison of powder patterns recorded at different wavelengths

Hello Rietvelders

I want to compare graphically powder patterns of a phase which were recorded at 
different wavelengths. Therefore I'd like to overlay the patterns using 
d-values, calculated from their corresponding 2theta values. In the case of 
monochromatic X-rays it's trivial. But which wavelength should one use in the 
case of Kalpha1-Kalpha2 radiation (lab instrument)?

Thanks for your help.

Regards
Franz Werner

Tallinn University of Technology
Estonia
-- 
GRATIS für alle GMX-Mitglieder: Die maxdome Movie-FLAT!
Jetzt freischalten unter http://portal.gmx.net/de/go/maxdome01

RE: zero-background quartz plates

[Kurt Leinenweber]

Hi All,
 
What's the big deal about making these plates?  Why don't we of the community 
make our own?
 
In particular, I have found that when using one of the "new" wide detectors, 
you really have to worry about the angle of the cut off any crystallographic 
axes, and some of the standard plates give HUGE backgrounds when used with wide 
or area detectors.
 
- Kurt



From: Mercier, Patrick [mailto:patrick.merc...@nrc-cnrc.gc.ca]
Sent: Mon 11/16/2009 12:28 PM
To: bill.l.re...@exxonmobil.com; rietveld_l@ill.fr
Subject: RE: zero-background quartz plates



Hello,

Check out the MTI Corporation website at the following URL:

http://www.mtixtl.com/index.asp?PageAction=VIEWPROD&ProdID=1431

They make both silicon and quartz zero-background holders.

Regards,
-Patrick

___
|Patrick H.J. Mercier, Ph.D., P.Phys., Eng. Jr
|Competency Leader, Ceramic Materials | Chef de compétence, Matériaux céramiques
|Research Officer | Agent de recherches
|Institute for Chemical Process and Environmental Technology
|Institut de technologie des procédés chimiques et de l'environnement
|National Research Council of Canada | Conseil national de recherches du Canada
|1200 Montreal Road, Ottawa, Ontario, Canada, K1A 0R6
|Tel: 613-993-7752 Fax: 613-991-2384 patrick.merc...@nrc-cnrc.gc.ca

RE: LP factor in the Rietveld refinement

[Kurt Leinenweber]

Hi all,
 
I haven't actually DONE this, so maybe I shouldn't put my 2 cents in, but can't 
you refine the polarization factor by using a standard such as Y2O3 and fixing 
the structure and thermal parameters of the standard while refining the 
polarization angle?
 
The angle so obtained should agree with what the theory tells you for your 
diffractometer configuration, but it seems more comforting to verify it by a 
measurement.
 
- Kurt



From: alor...@unex.es [mailto:alor...@unex.es]
Sent: Sat 7/25/2009 1:29 PM
To: Leonid Solovyov
Cc: rietveld_l@ill.fr
Subject: Re: LP factor in the Rietveld refinement



In this context:

What about the LP for a Goebel mirror followed by a 4-bounce or 2-bounce
primary monochromator?

Best regards

angel l. ortiz

>
> As far as I know, for X-ray mirrors the LP angle is near zero.
>
> 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
> ***
>
> --- On Sat, 7/25/09, chu...@hkusua.hku.hk  wrote:
>
>> From: chu...@hkusua.hku.hk 
>> Subject: Re: LP factor in the Rietveld refinement
>> To: "Ross H Colman" 
>> Cc: rietveld_l@ill.fr
>> Date: Saturday, July 25, 2009, 4:16 AM
>> Dear Ross,
>>
>> How about the LP factor/monochromator angle if using Gobel
>> mirror in 
>> my D8 system?
>>
>> Thanks!
>>
>> stephen
>>
>
>
>
>
>

Internal standard

[Kurt Leinenweber]

Hi all,

 

This may be a non-issue given the high accuracy of diffraction measurements, 
and the internal checks on sample position, such as dependent peaks that lead 
to the sample shift, but there is something I've always wondered about when an 
internal standard is used in combination with refinement.

 

You can fix the lattice parameter of silicon, as Patrick says below, but the 
extent to which this fixed lattice parameter enters the refinement depends on 
how much silicon is in the sample.  If you keep adding more silicon, in effect 
you are weighting the data to have an increasing dependence on the silicon.  
So, what is the correct ratio of silicon to unknown, to be sure that you are 
making the best measurement?

 

I suppose this is only an issue if the sample shift or zero error is quite 
large, in which case you might want to work on that problem first.  But still, 
it's something I've wondered about.

 

- Kurt

 

 

*

Kurt Leinenweber

Dept. of Chemistry and Biochemistry

Arizona State University

Tempe, AZ 85287-1604

 

phone (480)-965-8853

fax (480)-965-2747

 

***



From: Patrick Weisbecker [mailto:weis...@yahoo.fr] 
Sent: Thursday, May 14, 2009 10:16 AM
To: leopo...@fq.edu.uy
Cc: rietveld_l@ill.fr
Subject: Re : Introduction and Unit cell parameter determination

 

It is indeed advisable to start with an internal standard to check that there 
is no instrumental error or sample position issue (sample displacement is the 
more common cause of peak shift).

Silicon powder is often used as a standard, a standard reference material (SRM) 
is sold by the NIST (SRM640) but you can also use good quality silicon powder 
(99.99%) if you don't need an accuracy better than 0.0001A (a=5.4309A).

 

Rietveld programs are indeed not necessary if you only the lattice parameters, 
standard peak fitting and lattice parameter refinement using several peaks at 
high angle should give you good results.

 

Fullprof can handle internal standard: you have to fix the lattice parameter of 
Si to its known value and refine zero error or sample displacement parameter 
(use Full profile fit prerentially as indicated by Leopoldo).

 

Patrick

 



De : Leopoldo Suescun 
À : Gumelar Pritosiwi ; rietveld_l@ill.fr
Envoyé le : Jeudi, 14 Mai 2009, 15h45mn 16s
Objet : RE: Introduction and Unit cell parameter determination

Dear Gumelar Pritosiwi,

 

There are two independent topics in your question. If you are using a well 
calibrated conventional diffractometer to determine your cell parameters then 
you don't need an internal standard. That would be useful if you, additionally, 
need to do a quantitative phase analysis.

 

In a conventional machine with sealed tube source the cell parameters 
determination can be done easily in the case of cubic magnetite, because you 
already know the incident wavelength and d-spacings for the observed maxima are 
linearly related to "a" cell parameter by d(hkl)=a/sqrt(h^2+k^2+l^2).

 

Programs such as FULLPROF, GSAS, TOPAS, etc. are meant for Rietveld refinement, 
that is something a little bit more complex than cell parameters determination, 
although most of these programs have additional routines (peak search and 
indexing in Winplotr) that can help determine cell parameters of an unknown 
phase, or in your case, of the magnetite you are studying. You can also try 
full profile fit (LeBail or Pawley methods) to extract best possible cell 
parameters provided your data is of enough quality and you are willing to cope 
with profile shapes, background modeling, etc. (too complicated to start with 
in my opinion). 

 

If you use data with internal standard for lattice parameters determination you 
may choose to ignore the internal standard peaks or just collect new data on 
the raw material where you just see your magnetite peaks (be careful, if your 
sample contains other crystalline materials you will need to identify the extra 
peaks and avoid using them for the cell parameters determination).

 

Free programs like checkcell will allow you to determine your cell parameters 
by refinement of previously determined peak positions, other programs like 
Winplotr, PowderX, etc will allow you to perform a peak search and extract a 
peak list, other programs like CMPR can fit individual peaks and output a list 
of fit results. Any of these (and many more) you can then fit to obtain "a" 
using the abovementioned equation. There are probably many more free programs 
to do either thing more or less automatically so you should check the www or 
ccp14 site for information. 

 

If your magnetite show any kind of structural distortion this may be a bit more 
complex, but in that case you'll need to check some crystallography book to get 
a better idea of what can you do with your powder diffraction data and 

RE: cRs

[Kurt Leinenweber]

Hi all - 
 
The way I've thought about it is that when you fit the background in Rietveld, 
that is a kind of background removal.  But, it is done in conjunction with the 
peak fit, which means that you are closer to subtracting the "true" background 
(a mixture of the machine background plus any scattering from the sample that 
is not part of the Bragg reflections).  And, the statistics of the background 
removal is properly included in the error analysis of the fit.
 
Still, there is cross-talk between the background and the Bragg peaks even in 
Rietveld refinement.  That cross-talk should be partly accounted for by the 
correlation matrix of errors between the different fitting parameters.  But it 
can still detract from the structure if done poorly.
 
That's how I think of it - - does it sound right, all?
 
- Kurt



From: Maxim V. Lobanov [mailto:m_loba...@huntsman-nmg.com]
Sent: Tue 3/3/2009 11:35 PM
To: rietveld_l@ill.fr
Subject: RE: cRs




As far as I understand, the major issue is that BG subtraction changes the 
error statistics (accordingly, weights applied in calculating function to 
minimize...). It is also somewhat arbitrary how you choose the BG line - so, 
you can easily subtract part of Bragg contribution from base of peak - hence, 
bias the data. Most probably there are more things I didn't mention. So, of 
course it is preferable to fit BG with some suitable empirical function (e.g. 
Chebyschev polynomials).

However, some Rietveld programs do not have good selection of BG functions, and 
it is sometimes problematic to correctly fit the BG - so, I think in this case 
careful BG removal would be the only option. I'd like to use this opportunity 
to ask Fullprof experts: is the Chebyschev option finally implemented? Or 
otherwise what is the best option to model difficult (wavy) background with 
Fullprof?

Sincerely,
Maxim.

---
Dr. Maxim Lobanov
R&D Director
Huntsman-NMG
mailto: m_loba...@huntsman-nmg.com

*
If you encounter any difficulties
sending e-mails to the addresses in huntsman-nmg.com domain,
this could be due to the our spam filter malfunction.
In case of such an event please send a message to n...@fromru.com

Please note that the old domain nmg.com.ru does not exist anymore -
please update your address book accordingly


-Original Message-
From: matthew.row...@csiro.au [mailto:matthew.row...@csiro.au]
Sent: Wednesday, March 04, 2009 8:32 AM
To: olga.smirn...@hw7.ecs.kyoto-u.ac.jp
Cc: rietveld_l@ill.fr
Subject: RE: cRs


It's German... "verboten" == forbidden.

You should never delete the background from a diffraction pattern prior to 
(Rietveld) analysis.

It changes peak positions and shapes and generally is bad.


Cheers

Matthew


Matthew Rowles

CSIRO Minerals
Box 312
Clayton South, Victoria
AUSTRALIA 3169

Ph: +61 3 9545 8892
Fax: +61 3 9562 8919 (site)
Email: matthew.row...@csiro.au
-Original Message-
From: Olga Smirnova [mailto:olga.smirn...@hw7.ecs.kyoto-u.ac.jp]
Sent: Wednesday, 4 March 2009 16:30
To: Brian O'Connor
Cc: rietveld_l@ill.fr
Subject: Re: cRs

According to my computer, I received your response 4 minutes earlier
than forwarded the email.
What is 'verbotten' (volabulary does not find) ?
OS

Brian O'Connor wrote:
> Background removal is verbotten!
> Brian O'Connor
>
> 
>
> From: Olga Smirnova [mailto:olga.smirn...@hw7.ecs.kyoto-u.ac.jp]
> Sent: Wed 4/03/2009 2:14 PM
> To: rietveld_l@ill.fr
> Subject: cRs
>
>
>
> Dear All,
>
> How is life with conventional R factors when you always have to divide
> by zero background?
> Let's have time. Considering a part of the profile without peaks one
> gets 100% cR.
> I did not give the agreement factor; I would say those cR with all
> non-excluded points is incorrect, but cR for
> points with Bragg contribution is almost the same!
> Do you decrease the Rs by adding the background or do you increase cRs
> by subtracting the background?
>
> OS
>
> PS I did not ask my supervisor before sending such a mail.
>
>
>
>
>  
> 
>
> Internal Virus Database is out-of-date.
> Checked by AVG.
> Version: 7.5.519 / Virus Database: 269.21.6/1323 - Release Date: 3/10/2008 
> 11:07 AM
>  

error in peak positions that is linear in theta

[Kurt Leinenweber]

Dear Rietvelders,

 

(I hope this list is appropriate for this question).  I am trying to set
up a new D8 diffractometer from Bruker, and have it set up with a Vario
monochromator focusing on a sample in a capillary.  Of course I hope to
do Rietveld refinement on the samples eventually.  But there is an error
in two theta of the peak positions on all samples, and the error is
linear in two theta.  At 40 degrees the error (measured minus expected)
is about 0.020 degrees, at 80 degrees the error is about 0.040 degrees,
etcetera.

 

Has anyone ever seen anything like this and do you know where it could
come from?

 

Thank you very much,

 

- Kurt

 

 

*

Kurt Leinenweber

Dept. of Chemistry and Biochemistry

Arizona State University

Tempe, AZ 85287-1604

 

phone (480)-965-8853

fax (480)-965-2747

 

***

 

RE: Can anybody do me a favor to refine my Y2O3?

[Kurt Leinenweber]

Broad peaks... could the Y2O3 need to be annealed?  - Kurt



From: Leonid Solovyov [mailto:[EMAIL PROTECTED]
Sent: Fri 12/5/2008 8:14 AM
To: rietveld_l@ill.fr
Subject: Re: Can anybody do me a favor to refine my Y2O3?



Dear  Li,

I don't use GSAS, but I refined your data using the DDM program that gave 
nearly perfect fit. The DDM parameters file is attached and the program is 
freely available from
http://www.icct.ru/eng/content/persons/Sol_LA/ddm.html
or
http://www.geocities.com/l_solovyov/ddm.html

I must note, however, that the diffraction peaks in your pattern are very broad 
which may indicate a misalignment of your instrument or some problems with the 
X-ray tube. For this setup of X'Pert MPD the width of peaks below 60 degrees 
2theta should be less that 0.1, but your width is around 0.3 - too big!

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
www.geocities.com/l_solovyov
***

--- On Fri, 12/5/08, Mingtao Li <[EMAIL PROTECTED]> wrote:

> From: Mingtao Li <[EMAIL PROTECTED]>
> Subject: Can anybody do me a favor to refine my Y2O3?
> To: "Rietveld_l" 
> Date: Friday, December 5, 2008, 2:07 PM
> To all,
> I am learning rietveld refinement. First I want to
> get my
> instrumental parameter file. So I collected xrd pattern of
> cubic Y2O3
> on a X'pert pro MPD diffractiometer. The experimental
> conditions were
> listed as following:
>
> Cu KAlpha:
>KAlpha1:1.5405980
>KAlpha2:1.5444260
> ratio KAlpha2/KAlpha1:0.5000
>
> Incidental Beam Path:
>soller slit:0.02rad
>divergence slit 1 degree
>anti-scatter slit 2 degree
>incidental mask 10 mm
>
> Goniometer Radius 240mm
>
> Diffracted Beam Path
> antiScatterSlit: AS Slit 6.6mm
> sollerSlit:0.02rad
> filter:nickel (thickness:0.02mm)
> Detector:X'Celerator
>
> The xrdml attached is the original pattern file. The cif
> file of cubic
> Y2O3 and gsa file of the pattern are also attached.
>
> I have tried to do the refinement using GSAS many times
> following the
> instructions from http://www.cins.ca/cpdw/notes.html., but
> the results
> were quite different every time, especially the unit cell.
> Now I am
> very confused. Why did that happen? Shouldn't I refine
> S/L and H/L? So
> here I am for help. Can anyone do me a favor to refine my
> Y2O3 give a
> "standard" result?
>
> Thanks in advance.
>
> --
> **
> Mingtao Li, Ph.D. Candidate
> State Key Laboratory of Multiphase Flow in Power
> Engineering
> School of Energy and Power Engineering, Xi'an Jiaotong
> University
> No.28, Xianning West Road, Xi'an, Shaanxi, 710049, P.R.
> China
> Tel: +86-29-82668296-11  Fax:
> +86-29-82669033
> E-mail: mingtao dot li at gmail dot com
> **


  

RE: Quantitative analysis

[Kurt Leinenweber]

Dear Mario,

If the quantity of FeCO3 appears to be smaller than the actual value, then it 
could be due to absorption.  If you are using a copper source (CuKalpha) then 
that excites iron fluorescence, which is radiated equally in all directions... 
this means that the beam does not penetrate the FeCO3 particles entirely, and 
results in incomplete diffraction from these particles.

There are programs that correct for this problem, but as far as I know there is 
no freeware to deal with this effect.

- Kurt

 
*
Kurt Leinenweber
Dept. of Chemistry and Biochemistry
Arizona State University
Tempe, AZ 85287-1604
 
phone (480)-965-8853
fax (480)-965-2747
 
***

-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] 
Sent: Monday, October 27, 2008 8:48 AM
To: Rietveld_l@ill.fr
Subject: Quantitative analysis

Dear all,

I have this question,

I have been refined one mixture (of well-know percentage composition) of
CaCO3, CaF2, SiO2 and Al2O3, with preferential orientation in CaCO3 (104)
and CaF2 (111) with good results. When I add to the mixture FeCO3 and I
refine with preferential orientation (104), it happens that when I don´t
apply the preferential orientation in all this phases, I have correct
values of percentage composition, but when I apply the preferential
orientation the refinement is good but with incorrect values of percentage
composition. This experiment has been taken in Bragg Brentano geometry.
How I should refine this mixture?

Thanks a lot by your help.

Mario Macías
Universidad Industrial de Santander
Colombia

source for Y2O3?

[Kurt Leinenweber]

Dear Rietvelders,

 

In September there was a discussion of refining the polarization of an
instrument, and Lachlan and Matthew both suggested Y2O3.  The time has
come to do the measurement, and I was wondering if anyone has
suggestions for a good source and annealing schedule for the Y2O3?  Is
the already annealed material available as an XRD standard?

 

Thank you very much,

 

- Kurt

 

 

*

Kurt Leinenweber

Dept. of Chemistry and Biochemistry

Arizona State University

Tempe, AZ 85287-1604

 

phone (480)-965-8853

fax (480)-965-2747

 

***

 

RE: Beginer problems, difficulty charecterizing our diffractometer...

[Kurt Leinenweber]

Hi,
 
I am going to be in the same boat soon, especially regarding obtaining 
instrument parameters for a new instrument.  But one thing I do know, is that 
to get the polarization parameter, quartz is not a great standard.  For 
polarization factors, you need something really simple, with heavy atoms and 
all atoms on centers of symmetry, and with thermal parameters very well 
constrained, so that you can REFINE the polarization parameters for your 
machine, particularly when incindent beam monochromators are used.
 
The only problem is, I can't remember what the favorite standard is, or where 
it can be purchased.  I will need to know myself, so I will ask, on behalf of 
Blaise and myself as well, what is the best standard for refining the 
polarization of an instrument with monochromatized beam? Thank you!
 
- Kurt



From: Mibeck, Blaise [mailto:[EMAIL PROTECTED]
Sent: Wed 9/17/2008 12:22 PM
To: rietveld_l@ill.fr
Subject: Beginer problems, difficulty charecterizing our diffractometer...



 

I am re-learning GSAS to bring Rietveld to my department (for the first time). 
We have an old Phillips Xpert. 

 

I am trying to refine a quartz standard to acquire my profile and instrument 
parameters for this instrument and have yet to get my Chi^2 below 500. The 
instrument is not in my direct control. I have caught and asked them to correct 
a few problems already (dwell time too low, aluminum sneaking into the beam, 
etc...) and this has helped. I would like not to annoy them any more than I 
have too. 

 

At this point I think my high Chi^2s are mainly due to low angle asymmetric 
peaks that my fit is not able to copy - the asym is not terrible but may be 
messing me up. I am getting better results with peak profile functions 3 and 4, 
but unable to get Chi^2 below 500. My scans go up to 70 degrees 2theta.

 

I would like to tell the people caring for the instrument that my problem is on 
their end, but I am not confident in my own refining skills to say this. When I 
work with the tutorials or standard data from my graduate school experiment I 
am ok - I think I am proceeding in a reasonable way, although I can get stuck 
here and there. 

 

I would like to find out if I am doing something incorrectly or if the problem 
is instrument related. I hate to bug one of you but wonder if I could get 
someone to look at my work?? Is there a better forum for asking for this kind 
of help? 

 

Kindest regards to all of you,

Blaise

 

 

 

 

 

 

* * * * * * * * * * * * * 

Blaise Mibeck 

Research Scientist

Energy & Environmental Research Center

University of North Dakota

15 North 23rd Street, Stop 9018

Grand Forks, ND 58202-9018

 

Phone: (701) 777-5077

Email: [EMAIL PROTECTED]

 

 

 

RE: confusion about some GSAS parameters

[Kurt Leinenweber]

Hi all,
 
The GSAS manual is great, and so is GSAS - but in the case of IPOLA and IPOL, I 
have to admit that the GSAS manual is ambiguous, so I had to do the following 
recently when I had to set up a new diffractometer:
 
Do a Google search on the word IPOLA, and the first entry will be a wonderful 
discussion of the polarization parameters, including contributions from Bob Von 
Dreele, and I was able to set up my polarization correctly using that 
discussion.  Good luck!
 
- Kurt



From: Brian H. Toby [mailto:[EMAIL PROTECTED]
Sent: Thu 8/7/2008 10:04 AM
To: [EMAIL PROTECTED]
Cc: rietveld_l@ill.fr
Subject: Re: confusion about some GSAS parameters


On Aug 7, 2008, at 12:02 PM, [EMAIL PROTECTED] wrote:


So, for the case of a brag brenteno diffractometer without any 
monochromator, will the value for POLA should be fixed to zero??


There are two GSAS polarization models (read the manual!), but my recollection 
is that for IPOLA=0, POLA should be 0.5 when you have no monochromator or 
analyzer.


Brian

RE: RES: ADS

[Kurt Leinenweber]

Hi all,

This is an interesting discussion of quantitative phase analysis.  It sounds to 
me from what Pam is saying that we can calculate an esd for each phase if we 
know its particle size, and that the relative error would be larger for phases 
in smaller abundance.  If this is correct, then you could also repeat the 
physical experiment several times and get a variation of similar magnitude to 
the one that is calculated.  Is this what happens?  Pamela refers to the errors 
as being "worse" for minor phases, but they are what they are, and why not 
estimate them?

- Kurt

-Original Message-
From: Whitfield, Pamela [mailto:[EMAIL PROTECTED] 
Sent: Friday, May 30, 2008 7:30 AM
To: [EMAIL PROTECTED]
Cc: rietveld_l@ill.fr
Subject: RE: RES: ADS

Hi Rheinhard

The comments weren't aimed at you in particular!  We've been banging our heads 
against a brick wall about this stuff for some time, but not many in the cement 
community seem to be listening.

Anyway - there is a fundamental statistics problem with quantifying minor 
phases (of any symmetry) as the stats get worse with fewer diffracting 
crystallites.
The numbers that Deane Smith produced in terms of reproducibility of the quartz 
reflection dealt with a single phase system.  It doesn't take much to imagine 
(or at least I do) that things rapidly get worse in a multi-phase system where 
theoretically every phase should consist of a nice random powder, reducing the 
required average particle size even further.  It should follow then that the 
errors obtained with minor phases will be worse than major phases where the 
stats are better even without any other effects.  Maybe my logic is flawed but 
I don't think so!  Having said that it has been demonstrated that the situation 
isn't quite as bad practically as it is theoretically.

Pam 

-Original Message-
From: Reinhard Kleeberg [mailto:[EMAIL PROTECTED] 
Sent: May 30, 2008 10:10 AM
To: Whitfield, Pamela
Cc: rietveld_l@ill.fr
Subject: Re: RES: ADS


Hi Pam,
maybe a misunderstanding: I did not try to discuss the amount of 
"amorphous" material in cements. I'm aware of the problem, but a 
careful  Rietveld analysis with an internal standard should be able to 
determine at least the magnitude of the amorphous part. Even if not 
(e.g. if profile errors or structural uncertainties of the clinker 
phases do prohibit a reliable quantification of the amorphous), a 
systematic error of 7 instead of 5 wt% for a highly symmetric phase with 
well resolved peaks like periclase is neither acceptable nor 
unavoidable. And in my opinion a careful sample prep, measurement and 
Rietveld analysis (maybe with internal standard) should be able to 
perform better. I only tried to relativise Lubo's general denial of the 
potential of quantitative phase analysis to reach an accuracy of about 1 
wt%. Maybe I'm simply more optimistic than Lubo ;-)
Reinhard

Whitfield, Pamela schrieb:

> Hi Reinhard
>  
> Saying the words amorphous content and cement in the same breath is
> heresy in many circles!  Personally I think that it's a case of 'see 
> no evil, hear no evil'!
> Anyway, many moons ago we did yet another study on the amorphous 
> content in clinkers/cements and they can vary alot - we found up to 
> 20wt% in some.  The amount probably depends on the kiln conditions, 
> alkali metal content and quenching rate.
> Anyway don't take my word for it, Lerch and Brownmiller did a lovely 
> bit of work (sadly forgotten) in 1937 using quenching in mercury (?!) 
> and calorimetry yielding amorphous contents in clinker between 
> 10-28%.  The Ruland method has also been used to show significant 
> amorphous contents in the various components of cement.
>  
> In my opinion the cement companies are probably more interested in
> consistency rather than accuracy to track changes in their process.  
> Case in point - strictly speaking the XRF samples should be micronized 
> (or fused) as well as the XRD ones - the XRF errors from the matrix 
> effects of a 30micron cement in a pressed pellet are not exactly ideal.
>  
> I would agree that it's worth trying to push the boundaries of QPA.
> All is not lost for cements though - I saw the results of a test that 
> Mati Raudsepp did with a very messy synthetic mineral mixture that 
> looked completely ridiculous with the number of phases, but the result 
> matched the weighing figures quite nicely.
>  
> Pam
>
> --
> --
> *From:* Reinhard Kleeberg [mailto:[EMAIL PROTECTED]
> *Sent:* Fri 30/05/2008 5:36 AM
> *To:* rietveld_l@ill.fr
> *Subject:* Re: RES: ADS
>
> Hi Lubo,
> the difference between 6 and 7 % MgO is bigger than 15 % relatively, 
> thus the error by wrong re-scaling (e.g. if 10 % "amorphous" are
> missing) is smaller than the error discussed. And, if the "true" 
> content of periclase should be about 5 %, than a measured value of 7 % 
> is worth to be discussed to be a 

RE: Preferred orientation?

[Kurt Leinenweber]

Hi all,

 

This thread  gives me a chance to ask a question I've had for a long
time.  I've heard about these large chambers where you can mix your
sample with a binder and have it fall out as small powder spheres to
avoid preferred orientation in Bragg-Brentano geometry.  But, my samples
are mostly between 10 and 50 milligrams in size. Does anyone know a way
to mount them without preferred orientation?  Thank you!

 

- Kurt

 

 



From: Whitfield, Pamela [mailto:[EMAIL PROTECTED] 
Sent: Thursday, May 08, 2008 9:16 AM
To: Kurt Leinenweber
Subject: RE: Preferred orientation?

 

It's one of the classic needle-shaped materials - it gives lovely SEM
images if you can avoid charging

 

From: Kurt Leinenweber [mailto:[EMAIL PROTECTED] 
Sent: May 8, 2008 12:12 PM
To: Whitfield, Pamela
Subject: RE: Preferred orientation?

 

HI Pamela/all,

 

This sounds intriguing.. why is wollastonite a problem in capillary
transmission?  Is it needle-like?

 

- Kurt

 



From: Whitfield, Pamela [mailto:[EMAIL PROTECTED] 
Sent: Thursday, May 08, 2008 7:55 AM
To: rietveld_l@ill.fr
Subject: RE: Preferred orientation?

 

I do that myself but it doesn't always help much if you've got something
like wollastonite! :-)

 

From: Martin [mailto:[EMAIL PROTECTED] 
Sent: May 8, 2008 10:51 AM
To: rietveld_l@ill.fr
Subject: RE: Preferred orientation?

 

Forget all that long winded stuff. Just collect the data on capillary
transmission geometry and avoid all (well, most of) the fuss.
 
Martin Vickers



Get fish-slapping on Messenger! Play Now
<http://clk.atdmt.com/UKM/go/msnnkmgl001008ukm/direct/01/> 

RE: advice on new powder diffractometer

[Kurt Leinenweber]

Hi all,

I never thought of background as "noise" - to me the noise should be
defined as the esd of the background points.  You could get that by
averaging 10 or 20 background points and getting the standard deviation.
I'm told that for typical counting statistics, that should be close to
the square root of the background, so Mike's idea of using that square
root seems reasonable.

- Kurt

-Original Message-
From: Alan Hewat [mailto:[EMAIL PROTECTED] 
Sent: Tuesday, February 19, 2008 3:10 AM
To: rietveld_l@ill.fr
Subject: RE: advice on new powder diffractometer

> So my question remains: what is the definition of signal to noise
ratio
> that is accepted for powder diffraction?

Why does it matter? A higher Bragg/Background ratio does not necessarily
mean better data if counting statistics are poor. Exaggerating slightly
:-) consider a single peak with a ratio of 100/1 compared to a peak with
a
ratio 1/1000. The second measurement will give the lowest error, not
the first which has a much higher signal/noise. And you measure lots of
points on a slowly varying background, so you have a much better
estimate
of background than the normal error of a single point. Please don't
encourage people to simply maximise "signal/noise".

Similarly, low profile R-factor's can be obtained with low resolution
data
and high background. That does not mean that low resolution data
produces
smaller errors in structural parameters.

I worry about people treating measurement and refinement as black boxes
with simplified measures of quality such as R-factors, signal-to-noise
etc. You have to look at the physical reality of the model and the
estimated errors in its parameters, while not cheating by removing data
that doesn't fit for unknown reasons, adding too much "a priori"
information such as constraints, or throwing in extra garbage parameters
to improve the R-factors.
__
Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE
<[EMAIL PROTECTED]> +33.476.98.41.68
http://www.NeutronOptics.com/
__

RE: advice on new powder diffractometer

[Kurt Leinenweber]

Hi Bob,

The band of delt/sig is a little wider than that, but I think the real
problem is that they sent me the data in cps.  I am awaiting the data in
counts now.  Thanks to you and others for pointing this out.

However, in my view, having the data in cps should simply go into the
histogram scale factor and should not affect the fit.  What is wrong
with my logic?

Thanks,

- Kurt



-Original Message-
From: Von Dreele, Robert B. [mailto:[EMAIL PROTECTED] 
Sent: Friday, February 15, 2008 6:37 AM
To: rietveld_l@ill.fr
Subject: RE: advice on new powder diffractometer

Hi Kurt,
If you plot the results in POWPLOT & do the "statistical analysis" what
does the delt/sig vs 2-theta plot look like? If weights are right then
the band of delt/sig ought to be roughly 2-3 sig wide. Is your data in
cpm? Some instruments make that by default. That will mess up the
R-factors.
Bob

PS RE: advice on new powder diffractometer

[Kurt Leinenweber]

Dear Rietvelders:

P.S.  I should mention that with that background of only 2 counts, the
maximum signal was around 2000 counts.

Thanks to everyone for all the help so far.

- Kurt

-Original Message-
From: Jon Wright [mailto:[EMAIL PROTECTED] 
Sent: Friday, February 15, 2008 4:05 AM
To: rietveld_l@ill.fr
Subject: Re: advice on new powder diffractometer

Kurt Leinenweber wrote:
> ... with wRp of 25% and crystallographic R also near 25%  ..

Maybe the background is too low :-?

Jon

RE: advice on new powder diffractometer

[Kurt Leinenweber]

Hi Jon,

Funny you should mention the background... it was very low, as you say.
Above 30 degrees the background averaged only 2 counts, with a minimum
of 1 count and a maximum of 3 counts, throughout the rest of the
spectrum.  Scan time was 2 hours.

I also found that there was some kalpha2 in the spectrum, with Ka2/Ka1 =
0.05. 

- Kurt


-Original Message-
From: Jon Wright [mailto:[EMAIL PROTECTED] 
Sent: Friday, February 15, 2008 4:05 AM
To: rietveld_l@ill.fr
Subject: Re: advice on new powder diffractometer

Kurt Leinenweber wrote:
> ... with wRp of 25% and crystallographic R also near 25%  ..

Maybe the background is too low :-?

Jon

advice on new powder diffractometer

[Kurt Leinenweber]

Hi All,

I am attempting to assist others to choose a new powder x-ray
diffractometer.  We are currently looking at a Panalytical X'Pert Pro in
alpha-1 configuration, and I would like to know if anyone has any
experience with this for Rietveld refinements?  For other reasons we
would like to keep the sample flat, but then we could not use the
alpha-1 configuration, so instead we would consider a "hybrid"
monochromator - I would like to ask if this monochromator makes it
impossible to do Rietveld?  Also, any other insights and suggestions for
systems that are competitive with these would be welcome.  We are at an
early stage and have time to think about this, will be looking at other
possibilities, and I would appreciate any suggestions.

Incidentally, I received some data on quartz (supplied by me) from the
alpha-1, and refined it using GSAS.  The refined structural and thermal
parameters are fine, but I get strange r-factors, with wRp of 25% and
crystallographic R also near 25%, chi**2 of 0.5.  Does anyone know why
this might happen?  With my old Siemens D5000 I easily get down to 10%
or better in the r-factors right away, so something obvious must be
wrong.

Thank you,

    - Kurt Leinenweber

RE: glass & crystalline

[Kurt Leinenweber]

Hi Lubo,

Yes, one way to do this is to add a known mass X of a standard (say
alumina) to a known mass Y of the glass + crystal sample, giving a
weight ratio f = X/Y of standard to sample.  Then use x-ray diffraction
to get the weight ratio of the standard to only the crystalline part of
the sample.  This should be a larger number, call it f'.  The ratio f/f'
is then equal to the mass fraction crystal/(crystal + glass) in the
sample.

I have seen this neat trick work well for calculating the quantity of
glass in a ceramic insulator for a power line.  The fraction of glass
calculated with this method was consistent with the SEM images of the
ceramic.

Hope that helps!

- Kurt



.  
-Original Message-
From: Lubomir Smrcok [mailto:[EMAIL PROTECTED] 
Sent: Saturday, February 02, 2008 4:09 AM
To: rietveld_l@ill.fr
Subject: glass & crystalline 

Hello,
I was asked by my colleague if there is a way how to find (I'd prefer 
estimate) 
the amount of the crystalline phase in the glass "matrix". Both phases
have the 
same (or very close) chemical composition.
If necessary, they can also prepare the sample totaly crystalline
without any 
glass.
My apologies for sending this problem to "rietveld" list, but I hardly
know any 
better address :-)
To be frank : I do not expect to solve the problem using "Rietveld" as
the 
structure of the crystalline phase is not very well known. They would
prefer a 
relatively simple method for daily use in their lab.
Thanks on behalf of them.
Lubo

RE: Re: peaks splitting

[Kurt Leinenweber]

Hi all,

All I can think of is an exsolution of some type.  But, this seems
difficult to imagine at a low temperature such as this.

- Kurt

-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] 
Sent: Tuesday, May 22, 2007 12:29 PM
To: Jon Wright
Cc: rietveld_l@ill.fr
Subject: Re: peaks splitting

OOOPSSS! True: 006 can't split!
I just overlooked the hkl's of the split peak.
Needless to say, I should have read the message more carefully...
Norberto Masciocchi

Quoting Jon Wright <[EMAIL PROTECTED]>:

> Hi everyone,
>
> Three responses saying it might be a lower spacegroup? I wonder if the
> emperors have their clothes on today?
>
> (006) reflections can't split in R-3c as they only have a multiplicity
> of 2 in the first place (0,0,6 and 0,0,-6). You were lucky enough to
> split (00l) which rules out any lattice distortion. Or lots of people
> are about to shout at me.
>
> Either a paper about "phase segregation" or an experimental artifact
> like a temperature instability. Or both!
>
> Cheers,
>
> Jon
>
> [EMAIL PROTECTED] wrote:
>> Dear all
>> I need your kind help
>> I am investigating a trigonal system. I collected neutron diffraction
>> patterns at T=300K and T=4K.
>> The data at T=300K can be nicely fitted with the spg R-3c.
>> At T=4K again I can described the data with the spg R-3c, but I   
>> noticed that now
>> the peaks with a larger c-axis component (see the (006) peak picture
in
>> attachment) are splitted in two: it is like as at low temperature   
>> there are two
>> phases with different c-axis (10.5838 and 10.566 Amstrong) and same
a-axis.
>> I don't think that the sample is chemically phase separated because
at room
>> temperature the (006) reflection is clearly a single peak. The
splitting
>> appears only at low temperature.
>>
>> Could anyone suggest me any possible explanation of this splitting
(lattice
>> distortion, modulation, etc)? Could be possible a triclinic
distortion?
>>
>> I don't know how to fit the data at T=4K. Should I change the space
group
>> because now I have two peaks while the R-3c gives me only one peak?
Then by
>> which criteria should I choose the new space group?
>>
>> thank you very very very much for your advices
>>
>>
>> best regards
>>
>> Stefano Agrestini
>>
>> Physics Department
>> The University of Warwick, UK
>>
>> 
>> This message was sent using IMP, the Internet Messaging Program.
>>
>>
>>

>>




This message was sent using IMP, the Internet Messaging Program.

Re: Structure dissemination

[Kurt Leinenweber]

Hi Rietvelders,

OK, I should have used my Webster's dictionary to begin with ... but I 
belatedly looked it up.  I meant to write "cognoscente," which comes from 
Italian (originally from the Latin "to know") and is used a lot here in the 
States, but to complicate matters, the Dictionary says that the modern Italian 
spelling is "conoscente" (can any of our Italian colleagues verify that?).

Thank you for all this fun discussion, but I will be sure to use my dictionary 
the next time I post to this list.

        - Kurt


---

Kurt Leinenweber
Department of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone:  (480)-965-8853
Fax: (480)-965-2747

---

-Original Message-
From: Dr.Ibrahim Odeh [mailto:[EMAIL PROTECTED]
Sent: Wednesday, June 07, 2006 2:43 PM
To: rietveld_l@ill.fr



  Did you mean this
  cog·no·scen·ti [ kògn? shéntee, kònny? shéntee ]
   (singular cog·no·scen·te [ kògn? shéntay ])


  plural noun

  Definition:

  connoisseurs or experts: people who have a refined and superior 
knowledge of a subject, especially the arts


Ibrahim Odeh
Physics Department
Yarmouk University
Irbid 211-63
Jordan
Tel. 962 2 721 ext.2300
E-mail:[EMAIL PROTECTED]
----- Original Message - 
From: "Kurt Leinenweber" <[EMAIL PROTECTED]>
To: 
Sent: Wednesday, June 07, 2006 8:57 PM


> Thanks for the correction!  - Kurt
>
>
> ---
>
> Kurt Leinenweber
> Department of Chemistry
> Arizona State University
> Tempe, AZ  85287-1604
>
> Phone:  (480)-965-8853
> Fax: (480)-965-2747
>
> ---
>
> -Original Message-
> From: Simon Billinge [mailto:[EMAIL PROTECTED]
> Sent: Wednesday, June 07, 2006 11:26 AM
> To: rietveld_l@ill.fr
>
>
> shouldn't that be a cogniscento (or cogniscenta)?
>
> S
>
> Kurt Leinenweber wrote:
>> Hi all,
>>
>> It's interesting to me that so many well-intentioned scientific questions 
>> are met with the response, "why don't you check the FAQ and get back to 
>> us when you are a cognescenti," and yet the political question of what is 
>> legal or illegal to transfer always elicits a very enthusiastic 
>> discussion.
>>
>> - Kurt
>>
>> ---
>>
>> Kurt Leinenweber
>> Department of Chemistry
>> Arizona State University
>> Tempe, AZ  85287-1604
>>
>> Phone:  (480)-965-8853
>> Fax: (480)-965-2747
>>
>> ---
>>
>>
>
> -- 
> Prof. Simon Billinge
> Department of Physics and Astronomy
> 4268 Biomed. Phys. Sciences Building
> Michigan State University
> East Lansing, MI 48824
> tel: +1-517-355-9200 x2202
> fax: +1-517-353-4500
> email: [EMAIL PROTECTED]
> home: http://nirt.pa.msu.edu/
>
>
>
> -- 
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.1.394 / Virus Database: 268.8.1/355 - Release Date: 6/2/2006
>
> 


This email and any files transmitted with it are confidential and intended 
solely for the use of the individual or entity to whom they are addressed. 
If you have received this email in error please notify the system manager. 
This message contains confidential information and is intended only for the 
individual named. 
If you are not the named addressee you should not disseminate, distribute or 
copy this e-mail. 

Re: Structure dissemination

[Kurt Leinenweber]

Thanks for the correction!  - Kurt


---

Kurt Leinenweber
Department of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone:  (480)-965-8853
Fax: (480)-965-2747

---

-Original Message-
From: Simon Billinge [mailto:[EMAIL PROTECTED]
Sent: Wednesday, June 07, 2006 11:26 AM
To: rietveld_l@ill.fr


shouldn't that be a cogniscento (or cogniscenta)?

S

Kurt Leinenweber wrote:
> Hi all,
> 
> It's interesting to me that so many well-intentioned scientific questions are 
> met with the response, "why don't you check the FAQ and get back to us when 
> you are a cognescenti," and yet the political question of what is legal or 
> illegal to transfer always elicits a very enthusiastic discussion.
> 
>       - Kurt
> 
> ---
> 
> Kurt Leinenweber
> Department of Chemistry
> Arizona State University
> Tempe, AZ  85287-1604
> 
> Phone:  (480)-965-8853
> Fax: (480)-965-2747
> 
> ---
> 
> 

-- 
Prof. Simon Billinge
Department of Physics and Astronomy
4268 Biomed. Phys. Sciences Building
Michigan State University
East Lansing, MI 48824
tel: +1-517-355-9200 x2202
fax: +1-517-353-4500
email: [EMAIL PROTECTED]
home: http://nirt.pa.msu.edu/

RE: Re: Structure dissemination

[Kurt Leinenweber]

Hi all,

It's interesting to me that so many well-intentioned scientific questions are 
met with the response, "why don't you check the FAQ and get back to us when you 
are a cognescenti," and yet the political question of what is legal or illegal 
to transfer always elicits a very enthusiastic discussion.

    - Kurt

---

Kurt Leinenweber
Department of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone:  (480)-965-8853
Fax: (480)-965-2747

---

Re: converting D8focus data

[Kurt Leinenweber]

Well, I was basing my information on what the company that sells Jade told
me.

- Kurt

- Original Message - 
From: "A. van der Lee" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, December 08, 2004 3:17 AM


On 7 Dec 2004 at 12:23, Kurt Leinenweber wrote:

>
> Bruker's data format is a binary, proprietary format.  Programs such as
Jade
> that can read it are written by clever programmers who were able to hack
> into the Bruker format.  However, the only source I have found for free
> programs is from Bruker itself.
>
What does this mean exactly, proprietary format? That it is secret? I
am not a very clever programmer, but with the aid of Bruker's own
manual for their data file conversion utility XCH (to which I
referred one or two days ago), Appendices A-C, in which the binary
format is explained in detail, I am able to write a conversion
utility .raw to .gsas myself in a couple of hours. I did the same
thing for the conversion of Bruker peak list files (.dif) to Crysfire
.cdt files. This utility is now distributed with the Crysfire
distribution.
And I am not the only one who did this. The LMPG suite of programs
(Jean Laugier) are all capable to read in Bruker raw files.

Arie
***
A. van der Lee
Institut Européen des Membranes (UMR 5635)
Université de Montpellier II - cc 047
Place E. Bataillon
34095 Montpellier Cedex 5
FRANCE

visiting address: 300 Av. Prof. E. Jeanbrau

tél.: 00-33-(0)4.67.14.91.35
FAX.: 00-33-(0)4.67.14.91.19
***

Re: converting D8focus data

[Kurt Leinenweber]

Dear All,

Unfortunately, I can't supply the program myself.  It came from Bruker (In
the US: 1-800-234-XRAY).  As I said, they sent it to me for free and I don't
see why they wouldn't give it to anyone who wants it.  Better yet, it might
be a newer version.  I think it will work for D500 data too.

Bruker's data format is a binary, proprietary format.  Programs such as Jade
that can read it are written by clever programmers who were able to hack
into the Bruker format.  However, the only source I have found for free
programs is from Bruker itself.

- Kurt

- Original Message - 
From: "William Bisson" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, December 07, 2004 9:58 AM


> Dear Kurt,
>
> Please may have a copy too? Will that work for D500 data?
>
> Regards
> William
>
> On Tue, 7 Dec 2004, Kurt Leinenweber wrote:
>
> > Bruker will send you their program raw2rawg for free on request.  It
works for converting their RAW files into GSAS files, at least on my D5000
system.
> >
> >- Kurt c
> >  - Original Message -
> >  From: Liliana Viciu
> >  To: [EMAIL PROTECTED]
> >  Sent: Monday, December 06, 2004 6:10 PM
> >  Subject: converting D8focus data
> >
> >
> >  Dear all,
> >
> >  I am collecting data with a Bruker D8focus diffractometer (.raw file)
and would like to use GSAS for Rietveld refinement. However, I was not able
to have the data converted in GSAS format. Is there any software able to
convert such a file to a gsas format file?
> >
> >  Any hint will be highly appreciated.
> >
> >  Thank you in advance,
> >
> >  Liliana
> >
> >
> >
> >  
> >
> >  Liliana Viciu, PhD
> >
> >  Chemistry Department
> >
> >  Princeton University
> >
> >  Princeton, NJ, 08544
> >

Re: converting D8focus data

[Kurt Leinenweber]

Bruker will send you their program raw2rawg for 
free on request.  It works for converting their RAW files into GSAS files, 
at least on my D5000 system.
 
        
                
                
    - Kurt c

  - Original Message - 
  From: 
  Liliana 
  Viciu 
  To: [EMAIL PROTECTED] 
  Sent: Monday, December 06, 2004 6:10 
  PM
  Subject: converting D8focus data
  
  
  Dear 
  all,
  I am collecting data with a Bruker D8focus diffractometer 
  (.raw file) and would like to use GSAS for Rietveld 
  refinement. However, I was not able to have the data converted in GSAS format. 
  Is there any software able to convert such a file to a gsas format file? 
  Any hint will be highly 
  appreciated.
  Thank you in 
  advance,
  Liliana
   
  
  Liliana Viciu, 
  PhD
  Chemistry 
  Department
  Princeton 
  University
  Princeton, 
  NJ, 
  08544  

solving the structure...

[Kurt Leinenweber]

Jasminka,

As someone who has never really solved anything hard but who dreams of being
able to, I am happy to meet you.

A good place to start is Armel LeBail's web page.  He has a nice description
of part of the process,

http://www.cristal.org/

and suggestions for some FREE software for solving structures from powder
data!

There is also another mailing list - the SDPD (Structure Determination from
Powder Diffraction) devoted to this topic.

- Kurt

- Original Message - 
From: "Jasminka Popovic" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, July 09, 2004 5:50 AM


Hi, let me introduce myself at the beginig. My name is Jasminka Popovic and
I am phd student at faculty of science university of zagreb. I did my
graduation theisis on structure determination of single crystals and till
know all the work I did regarding crystallography was single crystal
strucutre determination and refinement. Recenty I joined a powder
diffraction group at Institut of Rudjer Boskovic. I have learned (more or
less)how to to fitting, how to do indexing,  and how to refine structure
using rietveld method. But one thing is missing...I know how to "solve" and
refine when I have strucural model to start with...so I was wondering which
is the best method for obtaining the structural model when you have no clue
how the structure should look like...thank you all
Jasminka

--
Sudjelujte u Iskon Bonus nagradnom programu i osvajajte nagrade.
Saznajte više na web adresi http://www.iskon.biz/bonus/

Re: Next Endeavour version without Hofmann potential

[Kurt Leinenweber]

Thank you for this interesting discussion.  Does this also apply to the ICSD
database?  I have made tables from data taken from ICSD - am I going to go
to jail?

- Kurt


- Original Message - 
From: "Brian H. Toby" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Thursday, July 08, 2004 9:00 AM


> I have to agree with Vincent that I find aspects of CCDC's apparent
> actions troubling and warrant discussion even if all parties reach a
> happy agreement behind closed doors. If the CCDC claims partial
> ownership of everything derived from their database then how far does
> that go? Can they prevent someone from publishing an average bond
> distance mined from 10,000 structures? Do they require that the entire
> staff of the CCDC be included as coauthors?
>
> Alan is correct that there is much that we do not know: What information
> has Dr. Hoffmann has supplied only to Crystal Impact and what
> information is in the public domain?
>
> Since much is unclear, I will offer one possible argument on the CCDC's
> behalf. Academic researchers are given access to the CSD (and other)
> databases for academic (public) research at rates considerably reduced
> from that of commercial research. If someone makes a discovery from
> these "academic" facilities but rather than disclose it in the open
> literature, instead decides to use that information for private gain
> (either for the researcher or the employer's institution) then from my
> perspective this academic researcher/institution is "cheating" by paying
> academic rates, but performing commercial research. (I am not suggesting
> that I know this to be the case here).
>
> The CCDC is a valuable resource to our scientific community. The CCDC
> should take all steps needed to protect their intellectual property -- 
> which is their compilation of data (note anyone can compile their own
> data collection from the literature by "simply" typing in all the
> coordinates again), plus the wealth of tools they have built over the
> decades, as well as the comments and corrections they have created and
> include in their data collection. I think it reasonable that the CCDC
> forge agreements with organizations that would mine their data
> collection for profit.
>
> If on the other hand, the CCDC works to prevent the open publication of
> research results that derive from their data collection, or uses their
> size to prevent companies from producing software that competes with
> their own products, then I think they can no longer claim to be a
> non-profit organization "dedicated to the advancement of chemistry and
> crystallography for the public benefit..." (I am also not suggesting
> that I know this to be the case here).
>
> What exactly is the case here? I don't claim to know. I would hope that
> Dr. Hoffmann will publish all of his results from use of the CSD. At
> that point I would hope that the CCDC would not feel that algorithms or
> software that implements this public information is their intellectual
> property, unless developed within the CCDC. I will wait quietly and see
> what we learn over the months to come.
>
> Brian
>

Re: Defining the origin of P2/n

[Kurt Leinenweber]

Thanks 
Andreas.  I realized I was wrong when I drew a picture of how the glide 
plane and the 2-fold axis interact with the translational symmetry.  They 
make 4 points at +x +y +z, -x -y +z, +x +y -z, -x -y -z (2 pairs definitely 
related by a center of symmetry).  I should have done that before I posted 
to the list!
 
I am 
at home with newborn twins and have not had my hands on the blue book for 
several days.
 
    
- Kurt
---Kurt LeinenweberDepartment of 
ChemistryArizona State UniversityTempe, AZ  
85287-1604Phone:  (480)-965-8853Fax: 
(480)-965-2747--- 
-Original Message-From: Andreas Leineweber 
[mailto:[EMAIL PROTECTED]Sent: Wednesday, March 31, 2004 11:09 
AMTo: [EMAIL PROTECTED]Subject: Re: Defining the origin of 
P2/nThis problem can actually quite simply be solved 
without tables:There is the old rule (which crystrallographers a definitely 
able to prove) to obtain the crystal class:1.delete the Bravais type symbol 
(delete P in case of P2/n)2.substitute screw axes by the correspondingly 
oriented simple rotations (we already have a rotation, 2(1) becomes 
2)3.substitute glide planes by mirror planes with the same 
orientation.  (2/n becomes 2/m)This gives you the symbol of the crystal 
class/crystallographic point group.Thus you can see that P2/n belongs to the 
crystal class 2/m, which has a centre of inversion. All space group types 
belonging to a centrosymmetric crystal class have one or several Wyckoff 
sites with centre of inversion. Therefore, there must be a position (there are 
several ones) with fixed z coordinate.Andreas LeineweberKurt 
Leinenweber wrote:
Yes, but the atom doesn't have to sit there, unlike in the case of 2/m.  So,
GSAS has to fix z for one atom...

I don't have my International Tables with me, please correct me if I'm wrong
(there should be no sites with a fixed z parameter in P2/n).

			- Kurt


---

Kurt Leinenweber
Department of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone:  (480)-965-8853
Fax: (480)-965-2747

---

-Original Message-
From: Magnus H. Sørby [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, March 31, 2004 12:24 AM
To: [EMAIL PROTECTED]


Stephen and Kurt,

P2/n has a 2-fold axis perpendicular to a glide plane, so it does have fixed
points (unlike e.g. R3c).

Best regards,
Magnus H. Sørby


  
  -Opprinnelig melding-
Fra: Kurt Leinenweber [mailto:[EMAIL PROTECTED]]
Sendt: 31. mars 2004 08:55
Til: [EMAIL PROTECTED]
Emne: Defining the origin of P2/n


Stephen,

I think that P2/n has no fixed points, and in order to keep the whole
structure from shifting along the c-axis, one of the atoms has to be
arbitrarily fixed.  GSAS automatically fixes the first atom
z-parameter (was
your atom on the 2-fold symmetry axis?).  I remember this from
refining the
structure of high pressure FeTiO3 which had space group R3c.

- Kurt


---

Kurt Leinenweber
Department of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone:  (480)-965-8853
Fax: (480)-965-2747

---

-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, March 30, 2004 11:03 PM
To: [EMAIL PROTECTED]


Dear Rietvelders,

I used GSAS to refine my structure in P2/n, however the program
automatically
fixed the the XYZ positions of the first atom during refinement. To my
surprise, this atom is not seen in the "fixed atom list" in the atom
parameters
menu of GSAS.

Please advise and many thanks,

stephen











  

Re: Defining the origin of P2/n

[Kurt Leinenweber]

Sorry Allen - I guess this new generation of crystallographers really is as
bad as you think!

- Kurt


---

Kurt Leinenweber
Department of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone:  (480)-965-8853
Fax: (480)-965-2747

---

-Original Message-
From: Allen Larson [mailto:[EMAIL PROTECTED]
Sent: Wednesday, March 31, 2004 9:33 AM
To: [EMAIL PROTECTED]


[EMAIL PROTECTED] wrote:
>
> Dear Rietvelders,
>
> I used GSAS to refine my structure in P2/n, however the program
automatically
> fixed the the XYZ positions of the first atom during refinement. To my
> surprise, this atom is not seen in the "fixed atom list" in the atom
parameters
> menu of GSAS.
>
> Please advise and many thanks,
>
> stephen

I am amazed by the flow of miss information that flows on this list whenever
an
apparent problem with a space group comes up. I am forced to wonder if the
correspondents in these exchanges have ever looked at 'The International
Tables,
Volume A(1983)' or Volume 1(1969) or the earlier volume which dates in the
1930's. Or any of the several other treatises that can also serve as a
source
for this information.

The GSAS package contains a program, SpcGroup, that can be used to list the
symmetry operations of any possible string defining a possible space group.
In
general the space group symbol consists of 2 or more groups of characters
delimited by spaces. Please note that the spaces separating axial operations
are
required in the GSAS interpretation of the space group symbol. Thus 'R3c'
must
be written as 'R 3 c' or taking advantage of the fact that the lattice type
can
only occupy one character, 'R3 c', is accepted, but not recommended.

I might also note that all of this is based on the use of keyboards in
general
use in English speaking countries. And I did have no information concerning
what
you might get using other keyboards.

Now for P2/n is a centric space group for which there, in my mind, there
exists
no reasonable origin choice that the 1bar site. Therefore the software would
always choose that for the origin of the unit cell.

Allen C. Larson

Defining the origin of P2/n

[Kurt Leinenweber]

P2/n has a center of symmetry?  Please ignore my last post.  - Kurt


---

Kurt Leinenweber
Department of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone:  (480)-965-8853
Fax: (480)-965-2747

---

-Original Message-
From: Von Dreele, Robert B. [mailto:[EMAIL PROTECTED]
Sent: Wednesday, March 31, 2004 8:17 AM
To: [EMAIL PROTECTED]


Dear Stephen (& others),
I know there have been a number of replies to this since P2/n does have an
inversion center which is positioned at the unit cell origin. However, if
the space group is Pn (or P2) then the location of the origin is arbitrary
on one or more axes. GSAS does "automatically" handle this by forcing the
first and second atoms to have the opposite shifts for each of the arbitrary
axes. So in Pn the shifts for atom #1 will be sx,sy,sz and for atom #2 they
will be -sx,sy',-sz, i.e. the sx & sz shifts will be opposite but identical
for these two atoms while each will have it's own sy. Beware, different
damping applied to these atoms will make it drift as the applied shifts
won't be equal & opposite. If you do not want this to happen then put in
your own "hold" on the appropriate coordinates for one atom or else put in
your own constraint.
Bob Von Dreele



From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Wed 3/31/2004 12:02 AM
To: [EMAIL PROTECTED]



Dear Rietvelders,

I used GSAS to refine my structure in P2/n, however the program
automatically
fixed the the XYZ positions of the first atom during refinement. To my
surprise, this atom is not seen in the "fixed atom list" in the atom
parameters
menu of GSAS.

Please advise and many thanks,

stephen

Re: Defining the origin of P2/n

[Kurt Leinenweber]

Yes, but the atom doesn't have to sit there, unlike in the case of 2/m.  So,
GSAS has to fix z for one atom...

I don't have my International Tables with me, please correct me if I'm wrong
(there should be no sites with a fixed z parameter in P2/n).

- Kurt


---

Kurt Leinenweber
Department of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone:  (480)-965-8853
Fax: (480)-965-2747

---

-Original Message-
From: Magnus H. Sørby [mailto:[EMAIL PROTECTED]
Sent: Wednesday, March 31, 2004 12:24 AM
To: [EMAIL PROTECTED]


Stephen and Kurt,

P2/n has a 2-fold axis perpendicular to a glide plane, so it does have fixed
points (unlike e.g. R3c).

Best regards,
Magnus H. Sørby


> -Opprinnelig melding-
> Fra: Kurt Leinenweber [mailto:[EMAIL PROTECTED]
> Sendt: 31. mars 2004 08:55
> Til: [EMAIL PROTECTED]
> Emne: Defining the origin of P2/n
>
>
> Stephen,
>
> I think that P2/n has no fixed points, and in order to keep the whole
> structure from shifting along the c-axis, one of the atoms has to be
> arbitrarily fixed.  GSAS automatically fixes the first atom
> z-parameter (was
> your atom on the 2-fold symmetry axis?).  I remember this from
> refining the
> structure of high pressure FeTiO3 which had space group R3c.
>
>   - Kurt
>
>
> ---
>
> Kurt Leinenweber
> Department of Chemistry
> Arizona State University
> Tempe, AZ  85287-1604
>
> Phone:  (480)-965-8853
> Fax: (480)-965-2747
>
> ---
>
> -Original Message-
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
> Sent: Tuesday, March 30, 2004 11:03 PM
> To: [EMAIL PROTECTED]
>
>
> Dear Rietvelders,
>
> I used GSAS to refine my structure in P2/n, however the program
> automatically
> fixed the the XYZ positions of the first atom during refinement. To my
> surprise, this atom is not seen in the "fixed atom list" in the atom
> parameters
> menu of GSAS.
>
> Please advise and many thanks,
>
> stephen
>
>
>
>
>

Defining the origin of P2/n

[Kurt Leinenweber]

Stephen,

I think that P2/n has no fixed points, and in order to keep the whole
structure from shifting along the c-axis, one of the atoms has to be
arbitrarily fixed.  GSAS automatically fixes the first atom z-parameter (was
your atom on the 2-fold symmetry axis?).  I remember this from refining the
structure of high pressure FeTiO3 which had space group R3c.

- Kurt


---

Kurt Leinenweber
Department of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone:  (480)-965-8853
Fax: (480)-965-2747

---

-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Tuesday, March 30, 2004 11:03 PM
To: [EMAIL PROTECTED]


Dear Rietvelders,

I used GSAS to refine my structure in P2/n, however the program
automatically
fixed the the XYZ positions of the first atom during refinement. To my
surprise, this atom is not seen in the "fixed atom list" in the atom
parameters
menu of GSAS.

Please advise and many thanks,

stephen

Re: CIF to powder pattern

[Kurt Leinenweber]

Hi all,

With all the file converters floating around, what are the chances that we
are going to proliferate files with corrupted formats?  I have gotten some
files already that were supposed to be "GSAS files" but didn't have 80
columns, had blank lines, etc., and I assume they were made by file
converters that created the wrong format.  Has anybody else run into this?

I'm asking this because I myself want to write a file converter to add to my
program "Crystal Cracker," but I'm a little nervous about distributing it in
case I make mistakes in the output format.  Input is one thing, mistakes are
obvious, but output is quite another - the mistakes might not be noticed
until 3 AM at a beamline somewhere.

If anyone can think of a way to prevent this (standard open-source file
converters?) that would be great.

    - Kurt




---

Kurt Leinenweber
Department of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone:  (480)-965-8853
Fax: (480)-965-2747

---

-Original Message-
From: Armel Le Bail [mailto:[EMAIL PROTECTED]
Sent: Friday, March 05, 2004 10:54 AM
To: [EMAIL PROTECTED]


Hi,

 >Have you had any response to your query?  I also need to translate a CIF
 >file to hkl, d space and intensities.  Thank you.

No answer corresponding to a complete program doing directly
the job.

I received advice to use XTAL :
http://xtal.sourceforge.net/
or/and CIFTBX :
http://www.bernstein-plus-sons.com/software/ciftbx/

My own idea was to use either my own obsolete Rietveld
source code, removing useless parts and adapting the
entry to CIF files, or some Lazy-Pulverix code. I will do it,
but I don't know when (for translations from COD and PCOD
data)... It will be available as open-source (in a few months??).

Certainly, codes exist, but they are owned by crystallography-
related commercial companies or 'not for profit" ones.

Armel

PS - G. Courbion was informed about these NAC queries.
But this is week-end, be patient...

RE: Re: thermal parameters at low temperature

[Kurt Leinenweber]

Wait!  I have to mention - the "heaviness" of atoms (atomic number Z) is
important in x-ray diffraction, but is uncorrelated with the neutron
scattering factor for the nuclei.  When you say heavy, do you mean the
highly scattering ones for neutrons, or the high-Z ones?

- Kurt


-------

Kurt Leinenweber
Department of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone:  (480)-965-8853
Fax: (480)-965-2747

---

-Original Message-
From: Maxim V. Lobanov [mailto:[EMAIL PROTECTED]
Sent: Thursday, February 26, 2004 12:59 PM
To: [EMAIL PROTECTED]



>Sorry for the ambiguous information I gave previously. The data at
>room temperature were taken with a variable wavelength (TOF) whether
>at low temperature the data were recorded with constant wavelength.
>There is no magnetic contribution on the pattern. The negative thermal
>parameters are for the heaviest atoms in the crystal.
>
Then it seems that you really overlooked some instrumental issue that can
affect thermal factors. As pointed out by Andreas, indeed it would be most
critical for heavy atoms, with intrinsically low thermal factors at low T.
For example, absorprion. It is typically not very significant for neutrons,
but anyway I would calculate it (for example, using
http://www.ncnr.nist.gov/instruments/bt1/neutron.html), then fix in the
refinement and look if it would "cure" the thermal factors.

According to GSAS manual,
"For constant wavelength data the absorption coefficient, Ah, is related to
the value for 1е neutrons; the correction is indistinguishable from thermal
motion effects and should not be refined. "

By the way, I would be grateful if one could share the knowledge about some
other important instrumental factors, relevant for thermal factors in
neutrons, and ways to estimate reasonable correction values.
Sincerely,  Maxim.
__
Maxim V. Lobanov
Department of Chemistry
Rutgers University
610 Taylor Rd
Piscataway, NJ 08854
Phone: (732) 445-3811

Re: Bragg R and GSAS

[Kurt Leinenweber]

I tend to use bond lengths to check refinements.  If bond lengths - and
thermal parameters too - aren't physically reasonable, it can mean that the
structure is correct but the refinement is bad, that the structure is
somehow wrong, or the atom assignments are wrong.

Bond-valence sums are great for this purpose.  I use Eutax by Mike O'Keeffe
for this, but there are many other programs for bond-valence sums as well.

Philosophically, though, I sometimes get disturbed by the fact that the
structure has to agree with what we already know in order to be published.
It might be better not to think about this too much when doing
crystallography.

- Kurt


-------

Kurt Leinenweber
Department of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone:  (480)-965-8853
Fax: (480)-965-2747

---

-Original Message-
From: Jon Wright [mailto:[EMAIL PROTECTED]
Sent: Thursday, February 26, 2004 8:28 AM
To: [EMAIL PROTECTED]


In comparing refinements with different powder datasets there is no
"number of observations" in common usage and no 10:1 rule of thumb.
Broadly, this means "crappy" data with a chemically unreasonable model
can sometimes give much better figures of merit than a good structure
with "good" data.

Sad, isn't it?

Jon


Von Dreele, Robert B. wrote:

>Nandini,
>I suggest you look at the paper "Rietveld refinement guidelines", J. Appl.
Cryst. (1999) 32, 36-50.
>Bob Von Dreele
>
>
>-Original Message-
>From: Nandini Devi Radhamonyamma [mailto:[EMAIL PROTECTED]
>Sent: Thu 2/26/2004 8:38 AM
>To: [EMAIL PROTECTED]
>
>Thank you.
>In parallel with single crystal analysis, is there an
>accepted limit for R(F2) or any other parameter like
>Rexp to follow? I'm using synchrotron data.
>nandini
>
>
>

RE: RE: Re: thermal parameters at low temperature

[Kurt Leinenweber]

Title: RE: Re: thermal parameters at low temperature
ï


Liliana,
 
OK, 
they should vibrate less... but are they good neutron scatterers or poor?  
If they are poorly scattering, the thermal factors won't be as 
meaningful.
 
    
- Kurt
 
---Kurt LeinenweberDepartment of 
ChemistryArizona State UniversityTempe, AZ  
85287-1604Phone:  (480)-965-8853Fax: 
(480)-965-2747--- 
-Original Message-From: Marilena L Viciu 
[mailto:[EMAIL PROTECTED]Sent: Thursday, February 26, 2004 1:27 
PMTo: [EMAIL PROTECTED]Subject: RE: RE: Re: thermal 
parameters at low temperature
Kurt,
I mean heavy in the atomic number.
 
Liliana 

  -Original Message- From: Kurt Leinenweber 
  [mailto:[EMAIL PROTECTED] Sent: Thu 2/26/2004 2:21 PM To: 
  [EMAIL PROTECTED] Cc: Subject: RE: Re: thermal 
  parameters at low temperature
  Wait!  I have to mention - the "heaviness" of atoms 
  (atomic number Z) isimportant in x-ray diffraction, but is uncorrelated 
  with the neutronscattering factor for the nuclei.  When you say 
  heavy, do you mean thehighly scattering ones for neutrons, or the high-Z 
  ones?    
      
      - 
  Kurt---Kurt LeinenweberDepartment of 
  ChemistryArizona State UniversityTempe, AZ  
  85287-1604Phone:  (480)-965-8853Fax: 
  (480)-965-2747Original Message-From: Maxim 
  V. Lobanov [mailto:[EMAIL PROTECTED]]Sent: 
  Thursday, February 26, 2004 12:59 PMTo: 
  [EMAIL PROTECTED]>Sorry for the ambiguous information I 
  gave previously. The data at>room temperature were taken with a 
  variable wavelength (TOF) whether>at low temperature the data were 
  recorded with constant wavelength.>There is no magnetic contribution on 
  the pattern. The negative thermal>parameters are for the heaviest atoms 
  in the crystal.>Then it seems that you really overlooked some 
  instrumental issue that canaffect thermal factors. As pointed out by 
  Andreas, indeed it would be mostcritical for heavy atoms, with 
  intrinsically low thermal factors at low T.For example, absorprion. It is 
  typically not very significant for neutrons,but anyway I would calculate 
  it (for example, usinghttp://www.ncnr.nist.gov/instruments/bt1/neutron.html), 
  then fix in therefinement and look if it would "cure" the thermal 
  factors.According to GSAS manual,"For constant wavelength data the 
  absorption coefficient, Ah, is related tothe value for 1Ð neutrons; the 
  correction is indistinguishable from thermalmotion effects and should not 
  be refined. "By the way, I would be grateful if one could share the 
  knowledge about someother important instrumental factors, relevant for 
  thermal factors inneutrons, and ways to estimate reasonable correction 
  values.Sincerely,  
      
      
      
      
  Maxim.__Maxim V. LobanovDepartment 
  of ChemistryRutgers University610 Taylor RdPiscataway, NJ 
  08854Phone: (732) 
445-3811
<>

RE: diamond powder source

[Kurt Leinenweber]

About the "crystallinity" of amorphous Boron, even if it is a glass you
might get some strong and sharp x-ray peaks from the B-B bonds in the
icosahedra of boron atoms.  Does anyone know if this is the reason for
seeing strong peaks in the x-ray pattern of amorphous boron?

    - Kurt Leinenweber

-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]
Sent: Tuesday, July 31, 2001 3:53 AM
To: [EMAIL PROTECTED]
Subject: RE: diamond powder source


Actually, I checked out a reference for "amorphous boron", namely the CERAC
catalog. They apparently have a somewhat dubious definition of
crystallinity:

"typ. 5 microns aver. or less (essentially amorphous)"

Jens

-Original Message-
From: Madsen, Ian (Minerals, Clayton)
[mailto:[EMAIL PROTECTED]]
Sent: 30. juli 2001 01:17
To: '[EMAIL PROTECTED]'
Subject: RE: diamond powder source

Re: amorphous boron - at the time that we were looking for appropriate
diluents, we tried several different sources of boron, including some
specifically listed as "amorphous boron". At no time during these tests did
we find any boron that was remotely amorphous. All materials has strong
crystalline peaks and some had very complex XRD patterns, rendering them
unsuitable for use as a diluent.

Cheers

o--oo0oo---o
 Ian Madsen
>

RE: CCD Analysis in GSAS

[Kurt Leinenweber]

Sarah,

People usually average along circles around the center, correcting for
2*pi*r, to get the intensity as a function of two theta.  Whoever let you
use their CCD should have provided a program for you to convert the data
into a handy format such as GSAS.

- Kurt

-Original Message-
From: Sarah [mailto:[EMAIL PROTECTED]]
Sent: Monday, July 16, 2001 9:11 AM
To: [EMAIL PROTECTED]
Subject: CCD Analysis in GSAS


Hi,
I was hoping someone had dealt with this type of data before.  I am trying
to work with data obtained from a CCD.  I have x, y, and
z  coordinates.  Is it possible to perform an analysis with this set of
data, or must it first be compressed to a single line of position and
intensity?
Any help would be greatly appreciated.

Sarah Jurgensmeier
Penn State University
[EMAIL PROTECTED]

RE: new GSAS

[Kurt Leinenweber]

Anthony,

As far as I know, Windows only allows one unique program to automatically
open files with a particular extension.  :-{

Kurt L

-Original Message-
From: Anthony Manerbino [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, April 10, 2001 7:40 AM
To: '[EMAIL PROTECTED]'
Subject: RE: new GSAS


When 'registering' GSAS experiment files with the windows operating system
the file extension .exp is used when I register another routine such as
powpref I attempt to use the same extension (.exp).  The problem I'm
encountering is registering the extension .exp multiple times, are you only
able to link the extension to one subroutine at a time.

 Anthony M.

-

Re: GSAS on Virtual PC?

[Kurt Leinenweber]

Kaye (and others)

Did you get memory access violation errors when you tried to run expedt?
The same thing happened to me when I tried GSAS on the virtual PC.  It runs
fine on a regular PC.

- Kurt Leinenweber  

At 09:17 AM 3/21/00 -0800, you wrote:
>Has anyone successfully run GSAS using virtual PC (on Macintosh)? The
>program appears to be installed, i.e. launches and allows me to create a
>new experiment file, but will not run expedt (even though the extended
>menus appear after creating an experiment file).
>
>Any suggestions?
>
>Thanks, -Kaye
>
>Kaye Savage
>Dept. of Geological and Environmental Sciences
>Stanford University
>Stanford CA 94305-2115
>650-723-8017 ph
>650-725-0979 fax
>[EMAIL PROTECTED]
>
>
>
-

Kurt Leinenweber
Dept. of Chemistry
Arizona State University
Tempe, AZ 85287-1604

Ph. (480)-965-8853
Fax (480)-965-0474

-

Re: Suggestion on QPA?

[Kurt Leinenweber]

Matteo,

The error in the LST file is a statistical error that doesn't include
systematic errors.

Probably the largest of these systematic errors is an underestimation of
the weight fraction of a highly absorbing phase, for instance if you were
using copper radiation and had a first-row transition metal in your sample.
 In this situation the absorbing phase can be significantly underestimated
(several percent or higher errors are not uncommon). (Extinction in one or
more of the phases can also cause errors.)

Fortunately there is a nice trick to help with these problems.  Add, for
example, 40 weight percent of CaF2 (or another simple material with low
absorption) to your unknown sample.  Refine the weight fraction of CaF2.
If you get significantly less that 40 weight percent CaF2, the "missing
mass" can be accounted for by adding mass to the absorbing phase.

In cases I have tried, I also had density measurements from a pycnometer.
I found this to be a very useful independent check of the data.

I hope that helps.

    - Kurt Leinenweber 






At 06:41 PM 11/9/99 +0100, you wrote:
>
>Hello everybody!
>I am a new reader of this mailing list and an enthusiastic user of GSAS on
>XRPD though not still expert. I have the problem of estimating the wt%
>error of components of a multiphase mixture (that I made). Does anybody
>know how to calculate this error from the data given in the *.LST file? It
>seems that the error I get is too small (!), what could it be responsible
>for it?  Any suggestion or information about literature on the issue?
>Thanks
>
>Matteo Zoppi
>[EMAIL PROTECTED]
>
>
>
>

*
Kurt Leinenweber
Dept. of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone (480)-965-8853
Fax   (480)-965-0474

Advice on a new diffractometer

[Kurt Leinenweber]

Hi everyone,

There is a diffractometer here for rapid data collection (Siemens D5000,
7.5 degree position-sensitive detector, no monochromator and can't be
retrofitted for one).

My question is, what would be a good choice for a second diffractometer in
this situation (ie what brand, what kind of monochromators and detectors,
etc)?  I am hoping to be able to collect data that can be used to find unit
cells and do refinements, perform Monte Carlo solutions for complex phases,
etc.  The PSD system is not very good for this (it even has K-beta bumps
that come through the nickel filter!) Thanks!

    - Kurt Leinenweber

*
Kurt Leinenweber
Dept. of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone (480)-965-8853
Fax   (480)-965-0474

Thin samples in Bragg-Brentano geometry

[Kurt Leinenweber]

Rietvelders,

For a lot of small powder samples (say 10 milligrams) in Bragg-Brentano
geometry, the sample has to be spread very thin over the diffracting
surface of a slide in the diffractometer.  I notice that a lot of the
textbook formulas are for "infinitely thick" samples.  Is there a special
way to deal with the thin samples?  It seems like the absorption part of
the formula for peak intensities (for example, for phase fractions in
multiphase mixtures) will be changed.

    - Kurt Leinenweber

*
Kurt Leinenweber
Dept. of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone (480)-965-8853
Fax   (480)-965-0474

CIF format

[Kurt Leinenweber]

Rietvelders,

I notice that the new beta version of GSAS has a conversion to CIF format
under the Utilities heading (GSAS2cif).  Are other programs being made CIF
friendly as well?  Can I dump the extracted structure factors from GSAS
into ESPOIR, for example?  It would be nice if this was really happening...

- Kurt Leinenweber

*
Kurt Leinenweber
Dept. of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone (480)-965-8853
Fax   (480)-965-0474

Re: weight fractions in GSAS .LST file

[Kurt Leinenweber]

Hello all,

In my experience GSAS always reports the weght fractions - and their
uncertainties - in the .LST file, as long as you have 
atoms in all the phases, and are refining all but one of the phase
fractions under the selection L O S.

Has anyone else ever had the problem that Roger is asking about?

- Kurt Leinenweber


>How do I get GSAS to report weight fractions & their uncertainties in a
>.LST file? 
>Thanks,
>
>Roger Mason
>
>

*****
Kurt Leinenweber
Dept. of Chemistry
Arizona State University
Tempe, AZ  85287-1604

Phone (480)-965-8853
Fax   (480)-965-0474