Re: Misconduct

[Luca Lutterotti]



That’s the best message of the year!

I should remember it.

Luca


> On 16 Jan 2024, at 15:22, Alan W Hewat  wrote:
> 
> Ha ! When Terry Sabine proposed to call it Rietveld Refinement, I told him 
> that Rietveld was already "refined". 
> 
> 
> Dr Alan Hewat, NeutronOptics
> Grenoble, FRANCE (from phone)
> alan.he...@neutronoptics.com
> +33.476984168 VAT:FR79499450856
> http://NeutronOptics.com/hewat 
> ___
>
> 
> On Tue, 16 Jan 2024, 15:11 ,  > wrote:
>> Dear all,
>> 
>> I'm following this interesting discussion. It seems to me that sometimes 
>> there is an improper use of terminology, in particular when we talk 
>> about "profile refinement"; in reality, we all know that it is about 
>> "profile fitting". Or did I miss something?
>> 
>> sorry for the pedantry.
>> Alberto
>> ++
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>> ++
>> 
> ++
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> 

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Re: Misconduct

[Luca Lutterotti]

You are both true in a certain sense. It is true that this is not the core of 
the Rietveld refinement per se, but we don’t have an “official” term to call a 
refinement of a powder pattern using crystallographic parameters. Hence I tried 
to call it Rietveld-like or extended Rietveld.
The alternatives are full pattern fitting, but this is usually referring to an 
unconstrained refinement, Pawley like. In XRF they use the term Fundamental 
Parameters approach, but I am afraid in diffraction was already used (first 
Cohere, am I remembering right?) for fitting profiles using physical models for 
the instrumental broadening.
The Rietveld community never defined a generally accepted term for this kind of 
refinement, so people outside it what can they use?

I am amused how Armel can spot such articles and especially notice the trick 
they did. I would not call the worse Rietveld refinement but for sure a bad 
misconduct case. Were they removing some peaks they could not explain or put 
down an amorphous halo at low angle? I am sad they used Maud in the first place 
and then manipulate the image. I notice that they report the intensity as 
(linear) counts, but it is not, they replaced also the labels as from the 
noise, residual and peaks intensity I am sure it was in square root of the 
intensity. Background was removed too. But I think there was no review at all, 
as the figure caption contains errors even for the chemical formula (Fe -> F).

Best regards,
 <http://www.unitn.it/>

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




Maud: http://maud.radiographema.com <http://maud.radiographema/>


> On 13 Jan 2024, at 07:39, Alan W Hewat  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 <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 <http://neutronoptics.com/hewat>
>>> ___
>>>
>>> 
>>> On Fri, 12 Jan 2024, 12:57 Le Bail Armel, >> <mailto:le

Re: FPSM : (was Re: [EXT] [External] Re: Step-like basline)

[Luca Lutterotti]

To be more clear, they did not ask for anything except that such a paper should 
never be published!

Luca


 <http://www.unitn.it/>

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




Maud: http://maud.radiographema.com <http://maud.radiographema/>


> On 7 Sep 2023, at 10:13, Jonathan WRIGHT  wrote:
> 
> Hi Luca,
> 
> Thanks for sharing the links to your method - I hope we can try it the next 
> time we get stuck on identification.
> 
> It is a shame to hear you were delayed for so long by J.Appl.Cryst. Did they 
> ask  you to cite some work from the Glasgow group as the commercial 
> competitor? I have in mind that they were looking at measured profiles too 
> (https://doi.org/10.1107/S002188980400038X, 
> https://doi.org/10.1107/S0021889804011847).
> 
> Indeed I had overlooked your paper, so perhaps this list is still one of the 
> better ways to reach some parts of the powder diffraction community!
> 
> With best regards,
> 
> Jon
> 
> 
> 
> On 06/09/2023 18:52, Luca Lutterotti wrote:
>> I am glad you find FPSM an inspiring idea, me and my co-workers will be 
>> quite happy if this will results in some citations. The FPSM publication 
>> back in 2019 was a troubled submission. It took us more than 3 years as 
>> initially was just rejected (for economical reasons, as it would be unfair 
>> against the traditional search-match software developed by companies; you 
>> read it right, that was the reason for rejection by the reviewer and the 
>> editor accepted it even if the other reviewer was for accepting it as it 
>> is). We had some discussion, but no way. Then we tried to change journal 
>> (www were hesitant as it would have had much less visibility on the powder 
>> diffraction community) but finally Daniel discussed with another editor of 
>> the same journal and we re-submitted and got some fair reviewers. But it was 
>> long and the first rejection a bit shocking. I thought before you have to 
>> reject for scientific reasons…….
>> Now I am learning that not only at the academic level, but also some 
>> companies selling search-match software are including what they call WPF 
>> search-match, but no one cite the origin of the idea. I hope I don’t get a 
>> second Loopstra-Rietveld case….. ;-) Well in my case I wrote the software 
>> before publishing the idea.
>> That software was re-written from scratch to optimise for the speed and the 
>> method. That’s why we can work with several thousand structures at the same 
>> speed the other softwares work on less than hundreds. I did not use Maud for 
>> that in fact.
>> But I want you to know that the last version I developed on a recent EU 
>> project (not the one online), works also with turbostratic and modulated 
>> clay structures using your model (the Ufer et al.) to simulate them in the 
>> Rietveld. It is a fantastic trick that I use for texture analysis but also 
>> quantification and now in FPSM. Having a quick Rietveld help to search-match 
>> samples containing clays using data even at high angles (more than 60 degs). 
>> I indeed don’t pre-calculate and store structures because when you work with 
>> many of them it takes more time to load all the precalculations from a 
>> database (even the speedy ones) than to re-calculate everything.
>> So I am glad we both made use of each other models/ideas!
>> Best regards,
>> Luca
>> <http://www.unitn.it/>
>> logo_unitrento_firma.png
>> *
>> Luca Lutterotti*
>> Dipartimento di Ingegneria Industriale
>> Università di Trento
>> via Sommarive, 9 - 38123 Trento (Italy)
>> tel. +39 0461 2824-14 (Office), -34 (X-Ray lab)
>> ico_fb_32x32.pngico_twitter_32x32.pngico_insta_32x32.pngico_linkedin_32x32.pngico_youtube_32x32.png
>> Maud: http://maud.radiographema.com <http://maud.radiographema>
>>> On 5 Sep 2023, at 13:49, Reinhard Kleeberg 
>>>  wrote:
>>> 
>>> Dear Luca,
>>> I completely agree and will be very happy to have a 1D detector with 
>>> sufficient energy resolution to resolve a "pure" Cu Kalpha1/2 doublet from 
>>> W Lalpha1. This would make routine work much easier. IMHO, the biggest 
>>> improvements in XRPD instrumentation within the last decades came solely 
>>> from the detector side, should be continued.
>>> 
>>> Regarding search-match by Rietveld: Your FSPM method is a very inspiring 
>>> idea. Nicola Doebelin has incorporated a simplified approach in PROFEX, too:
>>> https://www.yout

Re: FPSM : (was Re: [EXT] [External] Re: Step-like basline)

[Luca Lutterotti]

No they did not, I think the reviewer was American, in fact he was also wining 
about unfair competition by the EU that provides funds to develop technologies 
directly competing against US companies…..
The FPSM was originally developed in 2013-2014 inside one EU project. I would 
have not developed it without in reality ;-)

Thanks Reinhard for the explanation of WPF related to Search-match. I can only 
see the advertisement/brochure and I didn’t know what exactly they do or mean 
with it.

Best regards,

Luca


 <http://www.unitn.it/>

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




Maud: http://maud.radiographema.com <http://maud.radiographema/>


> On 7 Sep 2023, at 10:13, Jonathan WRIGHT  wrote:
> 
> It is a shame to hear you were delayed for so long by J.Appl.Cryst. Did they 
> ask  you to cite some work from the Glasgow group as the commercial 
> competitor? I have in mind that they were looking at measured profiles too 
> (https://doi.org/10.1107/S002188980400038X, 
> https://doi.org/10.1107/S0021889804011847).

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

[Luca Lutterotti]

I am glad you find FPSM an inspiring idea, me and my co-workers will be quite 
happy if this will results in some citations. The FPSM publication back in 2019 
was a troubled submission. It took us more than 3 years as initially was just 
rejected (for economical reasons, as it would be unfair against the traditional 
search-match software developed by companies; you read it right, that was the 
reason for rejection by the reviewer and the editor accepted it even if the 
other reviewer was for accepting it as it is). We had some discussion, but no 
way. Then we tried to change journal (www were hesitant as it would have had 
much less visibility on the powder diffraction community) but finally Daniel 
discussed with another editor of the same journal and we re-submitted and got 
some fair reviewers. But it was long and the first rejection a bit shocking. I 
thought before you have to reject for scientific reasons…….

Now I am learning that not only at the academic level, but also some companies 
selling search-match software are including what they call WPF search-match, 
but no one cite the origin of the idea. I hope I don’t get a second 
Loopstra-Rietveld case….. ;-) Well in my case I wrote the software before 
publishing the idea. 
That software was re-written from scratch to optimise for the speed and the 
method. That’s why we can work with several thousand structures at the same 
speed the other softwares work on less than hundreds. I did not use Maud for 
that in fact.

But I want you to know that the last version I developed on a recent EU project 
(not the one online), works also with turbostratic and modulated clay 
structures using your model (the Ufer et al.) to simulate them in the Rietveld. 
It is a fantastic trick that I use for texture analysis but also quantification 
and now in FPSM. Having a quick Rietveld help to search-match samples 
containing clays using data even at high angles (more than 60 degs). I indeed 
don’t pre-calculate and store structures because when you work with many of 
them it takes more time to load all the precalculations from a database (even 
the speedy ones) than to re-calculate everything. 

So I am glad we both made use of each other models/ideas!

Best regards,

Luca

 <http://www.unitn.it/>

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




Maud: http://maud.radiographema.com <http://maud.radiographema/>


> On 5 Sep 2023, at 13:49, Reinhard Kleeberg  
> wrote:
> 
> Dear Luca,
> I completely agree and will be very happy to have a 1D detector with 
> sufficient energy resolution to resolve a "pure" Cu Kalpha1/2 doublet from W 
> Lalpha1. This would make routine work much easier. IMHO, the biggest 
> improvements in XRPD instrumentation within the last decades came solely from 
> the detector side, should be continued.
> 
> Regarding search-match by Rietveld: Your FSPM method is a very inspiring 
> idea. Nicola Doebelin has incorporated a simplified approach in PROFEX, too:
> https://www.youtube.com/watch?v=Oqj71TiifeI
> 
> I'm routinely applying a run of ~500 structures/minerals what we are commonly 
> using (+- the former QPA database of Seifert AUTOQUAN or from the BGMN 
> webpage) for a phase screening of unknown samples, needs ~ 5 min without 
> interaction. Than running QPA refinement with the best matching structures, 
> clicking on remaining peaks in the difference plot for getting a proposal of 
> best matching main line positions in the database, and adding these 
> structure(s) to the refinement, running again... This is a typical workflow 
> in our lab, no need for peak search, background treatment, thinking about 
> artifact peaks...
> 
> Best regards
> 
> Reinhard
> 
> Zitat von Luca Lutterotti  <mailto:luca.luttero...@unitn.it>>:
> 
>> Dear Reinhard and Rietvelders,
>> 
>> It is always a compromise. Ideally we would like the fastest instrument with 
>> a lot of intensity (so, 1D or 2D detectors) but no lines outside the Kalpha 
>> or even just the Kapha1 like the one of James Cline. But this means a 
>> monochromator on the incident beam and you get fluorescence background. Now 
>> I like your solution of the Si Drift detector, so you just cut the 
>> fluorescence and you don’t need the monochromator in the first place.
>> So we are working and we are testing some lab prototypes of a 1D Si Drift 
>> like detector to get the best of both world. It is only a lot of electronic, 
>> but one day we will have wonderful instrument with only the lines we need 
>> and no fluorescence for the background. Actually we use fluorescence for the 
>> chemical analysis (quantitative).
>> 
>> About the search-match proble

Re: Step-like basline

[Luca Lutterotti]

It is call graininess, as Miguel said before, these are mosaic single crystals 
and depending on your source (divergence, spot dimension at different angles 
etc.) you get each mosaic crystal to create a diffraction peak that especially 
at low two-theta angle may be displaced a lot from its theoretical position 
because it is diffracting from a non center position. This is what you get also 
when you analyse samples with extremely large grains. If you use a 2D detector 
instead of scanning with a point or small psd, you will see all these 
individual grain or mosaic crystals diffracting around their ideal spot or if 
it is a sample with just large grains, distributed around the Laue circle. More 
the grain is on a lateral position respect to the center of the beam, more it 
is displaced in two-theta. At higher angle your beam size on the sample is 
smaller and there is less displacement for geometrical reasons.
I like to work with 2D detectors (texture, stresses) because it is easy to see 
these “figures”.
In addition you have the spectral impurities identified by Frank and you may 
get some small grains with different orientation and twins that will create 
some of the non 00l peaks.
Analysing these kind of patterns would require a sophisticated simulation of 
the grains-crystals distribution and computing like ray-tracing for the 
geometrical effects. Not worth it. Single crystals and sharp textures requires 
a point beam to avoid these effects. And a monochromatic one.

Best regards,

Luca

 <http://www.unitn.it/>

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




Maud: http://maud.radiographema.com <http://maud.radiographema/>


> On 6 Sep 2023, at 17:43, Le Bail Armel  wrote:
> 
> Dear Frank,
> 
> Same as you. I have not a complete solution.
> 
> Best
> 
> Armel
> 
>> envoyé : 6 septembre 2023 à 16:57
>> de : Frank Girgsdies > <mailto:girgs...@fhi-berlin.mpg.de>>
>> à : Le Bail Armel mailto:le-bail.ar...@orange.fr>>
>> Cc: Rietveld_L mailto:Rietveld_L@ill.fr>>
>> objet : Re: Step-like basline
>> 
>> 
>> Dear Armel,
>> 
>> Thanks for this nice quiz!
>> 
>> However, after identifying the following spectral impurities:
>> Cu K_beta,
>> W L_alpha1,2
>> W L_beta1,2,3,4 and
>> W L_gamma1,
>> I am stuck now, leaving bout 1/2 to 1/3 of the tiny extra peaks 
>> unexplained.
>> 
>> Some of them look suspiciously like Cu K_alpha1+2 doublets and might 
>> thus belong to an impurity phase, or differently oriented crystallites 
>> of the main phase, which could lie as dust on the single crystal 
>> surface, but I had no luck trying to identify them.
>> 
>> Furthermore, the irregular high angle tailing of the 00l series (maybe 
>> stacking faults?) makes peak fitting difficult.
>> 
>> Thus, I give up (at least for now), hoping that you might disclose the 
>> solution to the riddle, as far as it is known, for us after a while.
>> 
>> Best wishes,
>> Frank
>> 
>> 
>> 
>> On 06.09.2023 10:47, Le Bail Armel wrote:
>> 
>>> Hi,
>>> 
>>> In the same subject.
>>> 
>>> A special "powder pattern" to play with (try to explain all peaks) :
>>> 
>>> http://cristal.org/muscovite.pdf <http://cristal.org/muscovite.pdf>
>>> 
>>> Best
>>> 
>>> Armel
>>> 
>>> 
>>> ++
>>> Please do NOT attach files to the whole list 
>>> Send commands to  eg: HELP as the subject with no body text
>>> The Rietveld_L list archive is on 
>>> http://www.mail-archive.com/rietveld_l@ill.fr/
>>> ++
>>> 
>> >
>> 
> ++
> Please do NOT attach files to the whole list  <mailto:alan.he...@neutronoptics.com>>
> Send commands to mailto:lists...@ill.fr>> eg: HELP as the 
> subject with no body text
> The Rietveld_L list archive is on 
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++

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++

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

[Luca Lutterotti]

Dear Reinhard and Rietvelders,

It is always a compromise. Ideally we would like the fastest instrument with a 
lot of intensity (so, 1D or 2D detectors) but no lines outside the Kalpha or 
even just the Kapha1 like the one of James Cline. But this means a 
monochromator on the incident beam and you get fluorescence background. Now I 
like your solution of the Si Drift detector, so you just cut the fluorescence 
and you don’t need the monochromator in the first place.
So we are working and we are testing some lab prototypes of a 1D Si Drift like 
detector to get the best of both world. It is only a lot of electronic, but one 
day we will have wonderful instrument with only the lines we need and no 
fluorescence for the background. Actually we use fluorescence for the chemical 
analysis (quantitative).

About the search-match problem. Have a look on our FPSM method (
http://fpsm.radiographema.com/) where we don’t care about extra lines as it is 
a Rietveld search-match. We don’t need to identify or search peaks. We don’t 
use peak positions, we just fit with the Rietveld. It is slower indeed, but 
every day is becoming faster and in a few years it will run quickly on our 
cellphones (I have a prototype running there).

Best regards,

Luca

 <http://www.unitn.it/>

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




Maud: http://maud.radiographema.com <http://maud.radiographema/>


> Begin forwarded message:
> 
> From: Reinhard Kleeberg 
> Subject: Re: [EXT] [External] Re: Step-like basline
> Date: 5 September 2023 at 08:56:15 CEST
> To: rietveld_l@ill.fr
> Reply-To: Reinhard Kleeberg 
> 
> Dear Luca,
> I completely agree with your opinion, and want to add that even for "trivial" 
> tasks in XRPD like phase analysis and standard Rietveld refinements the 
> satellites/spectral impurities do cause significant trouble:
> 
> - The K beta and W L satellites of strong peaks of major phases like quartz, 
> carbonates or cubic structures in geomaterials are typically not 
> automatically recognized in the standard peak search procedures and therefore 
> misinterpreted to be K alpha peaks and added to the peak list. I can't tell 
> you how often I was asked from colleagues for explanation of such 
> "unidentified peaks", and how much time people have spent for searching for 
> explanation of such artefact lines.
> - In Rietveld analysis our software must generate the peaks at least for the 
> measured angular range. Depending on the method how the software is doing 
> this, we run into problems with the satellites. If the software generates the 
> reflections from the positions of K alpha peaks from the start lattice 
> parameters and the (extended) upper measured angle, K beta satellites of K 
> alpha peaks outside this angular range will maybe not generated and remain 
> unfitted in the pattern. If the software generates the peaks depending on the 
> shortest wavelength in the wavelength profile (more intelligent approach), 
> the software must generate much more reflections (with maxima outside the 
> measured angular range) and all these peaks must be calculated over an 
> extremely broad angular range. In the case of low symmetry structures with 
> big cells or disordered structures described by partial structure factors and 
> the resulting extreme high numbers of peaks, the "extension effect" will 
> cause significantly prolonged time for calculations, without any positive 
> effect.
> 
> That's why I prefer to use instrumentation with better monochromatic 
> radiation (monochromators, high energy resolution detectors) even in the 
> daily business of phase analysis. We do use our 1D detector Mythen2 with Fe 
> filter (Co radiation) only for "quick and dirty" measurements.
> 
> Best regards
> 
> Reinhard
> 
> 
> Zitat von Luca Lutterotti :
> 
>> Dear Habib,
>> 
>> Reinhard is right, and what he explained is exactly what you observed. Now I 
>> would add that I may not define your Bruker clean and optimised, because for 
>> this kind of samples, wafers and extremely textured thin films, it would be 
>> better to have a monochromator in the incident beam and not a Ni filtered (I 
>> would more say it is a requirement). It was already showed many times in the 
>> past as a monochromator in the incident beam is a necessity for this 
>> materials to avoid all the "physical artifacts" created by the strong 
>> intensity and not clean Kalpha radiation.
>> 
>> Best regards,
>> 
>> Luca
>> 
>> <http://www.unitn.it/>
>> 
>> Luca Lutterotti
>> Dipartimento di Ingegneria Indus

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

[Luca Lutterotti]

Dear Habib,

Reinhard is right, and what he explained is exactly what you observed. Now I 
would add that I may not define your Bruker clean and optimised, because for 
this kind of samples, wafers and extremely textured thin films, it would be 
better to have a monochromator in the incident beam and not a Ni filtered (I 
would more say it is a requirement). It was already showed many times in the 
past as a monochromator in the incident beam is a necessity for this materials 
to avoid all the "physical artifacts" created by the strong intensity and not 
clean Kalpha radiation.

Best regards,

Luca

 <http://www.unitn.it/>

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




Maud: http://maud.radiographema.com <http://maud.radiographema/>


> On 4 Sep 2023, at 12:20, Habib Boughzala  wrote:
> 
> Many thanks Reinhard,
> 
> That's exactly what I wanted to say by  "I can assure that our Bruker D8 is 
> clean and optimized!"
> Otherwise, in some other cases of well conditioned thin film no similar 
> phenomenon is observed!
> So, yes, it's obviously possible that your point of view is right.
> 
> Regards
> Habib
> 
> 
> -- Message d'origine --
> De "Reinhard Kleeberg"  <mailto:kleeb...@mineral.tu-freiberg.de>>
> À "Habib Boughzala" mailto:boughz...@yahoo.com>>
> Cc rietveld_l@ill.fr <mailto:rietveld_l@ill.fr>
> Date 04/09/2023 11:07:50
> Objet Re: Re[2]: [EXT] Re: [External] Re: Step-like basline
> 
>> Dear Habib,
>> the phenomenom "satellites or edges" originates from the diffraction 
>> process. The critical parameters are:
>> - spectral pureness of the primary beam (primary beam monochromator, tube 
>> spectral contamination like W...)
>> - the use of K beta absorbtion filter (and its thickness)
>> - the energy resolution ("window") of the detector system.
>> Even a D8 system may be equipped with different types of detectors, slits 
>> and energy limits can be set differently for an identical configuration, and 
>> quite often satellite peaks may appear later in the time of use (aging of 
>> the tube produces more W L, Fe filters may corrode and get perforated...). 
>> So it is strictly recommended to check the instrument peridically, by 
>> measuring a full pattern of a profile standard (LaB6 or Si or similar).
>> Greetings
>> Reinhard
>>  
>> Zitat von Habib Boughzala mailto:boughz...@yahoo.com>>:
>>  
>>> Dear all,
>>> I would like to send you my witness related to this kind of observation.
>>> I can assure that our Bruker D8 is clean and optimized!
>>>  
>>> In many cases of well conditioned thin film (spin coating or controlled 
>>> diffusion) material this kind of phenomenon is visible around the highest 
>>> reflection, especially when the preferred orientation is drastically 
>>> present.
>>>  
>>> So, in my opinion, Reinhard and Alan are right, and what is observed is 
>>> just like reflections broadening, asymmetry, shifting ...etc ... and can be 
>>> related to the material behavior.
>>> Now, what is the physical (crystallographic!) property responsible of this 
>>> phenomenon? let's open the floor for a large discussion.
>>>  
>>>  
>>> Habib
>>>  
>>>  
>>> -- Message d'origine --
>>> De "Alan W Hewat" >> <mailto:alan.he...@neutronoptics.com>>
>>> À "Reinhard Kleeberg" >> <mailto:kleeb...@mineral.tu-freiberg.de>>
>>> Cc rietveld_l@ill.fr <mailto:rietveld_l@ill.fr>
>>> Date 04/09/2023 09:29:08
>>> Objet Re: [EXT] Re: [External] Re: Step-like basline
>>>  
>>>> Reinhard is right that it is best to improve the instrument to produce 
>>>> cleaner data. I'm concerned about the advice to model all kinds of 
>>>> features whose origin is not fully understood, simply to obtain a better 
>>>> fit. Shay has told us nothing about his instrument or his conditions of 
>>>> data collection. He asks "Is it a sample preparation problem", to which 
>>>> the obvious reply is "Do you see this with other samples or different 
>>>> materials" ? Only he can answer that. If the answer is yes, he might try 
>>>> modifying his instrument (remove filters etc) to see what effect that has 
>>>> on the pattern from a simple well characterised material. Again only he 
>>>> can do that. Data collecti

Re: Rietveld condamnation considered as established by some more people

[Luca Lutterotti]

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

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

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

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

Luca

 <http://www.unitn.it/>

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




Maud: http://maud.radiographema.com <http://maud.radiographema/>


> On 17 Aug 2023, at 10:40, Alan W Hewat  wrote:
> 
> Armel, it's not about you :-) But in your 1988 paper you did not reference 
> Pawley (1980) and even Rietveld only appeared as #14
> https://www.researchgate.net/publication/228084768_Ab_Initio_Structure_Determination_of_LiSbWO6_by_X_ray_Powder_Diffraction#fullTextFileContent
> 
> But let's not change the subject. You have published comments, linked to in 
> your opening post, accusing respected scientists of "Calumny... towards a 
> dead man who cannot defend himself". Simply because people who have direct 
> experience of the history (which is often about dead men) do not agree with 
> you. 
> 
> And yes, Columbus did not discover America either, but he contributed. Be 
> content with contributing, and let it go.
> 
> Regards Alan 
> 
> Dr Alan Hewat, NeutronOptics
> Grenoble, FRANCE (from phone)
> alan.he...@neutronoptics.com
> +33.476984168 VAT:FR79499450856
> http://NeutronOptics.com/hewat <http://neutronoptics.com/hewat>
> ___
>
> 
> On Thu, 17 Aug 2023, 17:49 Le Bail Armel,  <mailto:le-bail.ar...@orange.fr>> wrote:
>>> >And there are other examples. See this brief review of "Whole Pattern 
>>> >Fitting - The Pawley Method" (1980) yet few people now attribute this kind 
>>> >of profile refinement to Pawley. 
>>> >http://pd.chem.ucl.ac.uk/pdnn/solve1/pawley.htm
>>> 
>>> Few people ? At least me :
>> https://onlinelibrary.wiley.com/iucr/itc/Ha/ch3o5v0001/sec3o5o2o2o1/?
>> 
>> And 2168 papers cite the 1980 Pawley paper according to Google Scholar as of 
>> today.
>> 
>> Be more clear. What are exactly those other examples ?
>> 
>> ALB
>> 
> ++
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> ++
> 

++
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++

Re: Simultaneous refinement of multiple atoms sharing same site

[Luca Lutterotti]

With 3 atoms, as Larry and Alan explain it cannot be done unless you have 
additional info (e.g. chemical info). In our lab, if the three atoms or at 
least 2 are in the range for XRF, we do a combined XRD+XRF refinement.

Luca

---Luca 
Lutterotti
Dipartimento di Ingegneria Industriale, Universita' di Trento,
via Sommarive, 9, 38123 Trento, Italy

e-mail address : luca.luttero...@unitn.it <mailto:luca.luttero...@ing.unitn.it>
Maud page : http://maud.radiographema.com <http://maud.radiographema/>

Phone number :+39-0461-28-2414
XRD lab:: +39-0461-282434
Fax : +39-0461-28-1977





> On 31 Aug 2019, at 16:44, Ahmed Subrati  wrote:
> 
> Dear all,
> 
> I wanted to ask how three atoms, sharing the same xyz position, could be 
> refined in terms of their occupancies via FullProf. We know that for the case 
> of two atoms, the first atom is set as 11.0 and the second one as -11.0 so 
> that their sum is unity, but how would be the case for three atoms.
> 
> Thank you very much.
> 
> King regards,
> Ahmed Subrati
> PhD student
> NanoBioMedical Centre | Adam Mickiewicz University in Poznan, Poland
> ++
> Please do NOT attach files to the whole list  <mailto:alan.he...@neutronoptics.com>>
> Send commands to mailto:lists...@ill.fr>> eg: HELP as the 
> subject with no body text
> The Rietveld_L list archive is on 
> http://www.mail-archive.com/rietveld_l@ill.fr/ 
> <http://www.mail-archive.com/rietveld_l@ill.fr/>
> ++

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++

Re: Hippo wizard in Maud

[Luca Lutterotti]

Dear Carolina,

using Maud 2.79, the Hippo wizard works if you don’t select the option to 
“Treat rotations as separate…..”. That option was re-enabled recently on 
request but was not up to date with the rest of the program. The last version 
(2.81) of Maud corrects it. So, go to the Maud web site and download the last 
available version.

If you have a problem with that option unchecked, then it is something 
unexpected, may be depending on the datafiles. But if you are using Hippo 
datafiles, it should not, you may ask Sven. Actually he confirmed me that with 
the last version of Maud the wizard works with the option on.

Best regards,

Luca

---Luca 
Lutterotti
Dipartimento di Ingegneria Industriale, Universita' di Trento,
via Sommarive, 9, 38123 Trento, Italy

e-mail address : luca.luttero...@unitn.it <mailto:luca.luttero...@ing.unitn.it>
Maud page : http://maud.radiographema.com <http://maud.radiographema/>

Phone number :+39-0461-28-2414
XRD lab:: +39-0461-282434
Fax : +39-0461-28-1977





> On 29 Jun 2018, at 19:52, Carolina Corvalán  
> wrote:
> 
> Hi all,
> 
> I have some problems to read a file .gda (neutron diffraction from hippo) 
> with maud. The wizard doesn't work or maybe is my maud installation. I work 
> in windows 7, 64 bits, MAUD 2.79.
> Please let me know if someone has any idea,
> Thanks,
> 
> Carolina
> ++
> 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: Stoichiometry and occupancy fractions of solid solutions

[Luca Lutterotti]

Sorry, here is the direct link to the journal article if you have the 
subscription:

http://www.sciencedirect.com/science/article/pii/S0026265X15003756 
<http://www.sciencedirect.com/science/article/pii/S0026265X15003756>

Luca

---Luca 
Lutterotti
Dipartimento di Ingegneria Industriale, Universita' di Trento,
via Sommarive, 9, 38123 Trento, Italy

e-mail address : luca.luttero...@unitn.it <mailto:luca.luttero...@ing.unitn.it>
Maud page : http://maud.radiographema <http://maud.radiographema/>.com

Phone number :+39-0461-28-2414
XRD lab:: +39-0461-282434
Fax : +39-0461-28-1977




> On 20 Dec 2016, at 16:04, Cline, James Dr. (Fed) <james.cl...@nist.gov> wrote:
> 
> Luca,
>  
> I’d be interested to read your article, but I’m not about to join 
> researchgate to do so.
>  
> 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 <mailto:jcl...@nist.gov>
> (301) 975 5793
> FAX (301) 975 5334
>  
> From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On Behalf 
> Of Luca Lutterotti
> Sent: Tuesday, December 20, 2016 9:55 AM
> To: rietveld_l@ill.fr
> Subject: Re: Stoichiometry and occupancy fractions of solid solutions
>  
> To increase sensitivity to partial/mixed occupation and also solve the case 
> of 3 or more atoms in the same site (you have an infinite number of solutions 
> that give you the same scattering factor, both x-ray and neutrons) we are 
> developing a combined XRD-XRF analysis. Some preliminary application examples 
> were published and we are preparing a full article on the theory behind.
> https://www.researchgate.net/publication/288701415_Combined_X-Ray_diffraction_and_fluorescence_analysis_in_the_cultural_heritage_field
>  
> <https://www.researchgate.net/publication/288701415_Combined_X-Ray_diffraction_and_fluorescence_analysis_in_the_cultural_heritage_field>
>  
> Best regards,
>  
> Luca
>  
> ---Luca 
> Lutterotti
> Dipartimento di Ingegneria Industriale, Universita' di Trento,
> via Sommarive, 9, 38123 Trento, Italy
>  
> e-mail address : luca.luttero...@unitn.it 
> <mailto:luca.luttero...@ing.unitn.it>
> Maud page : http://maud.radiographema <http://maud.radiographema/>.com
>  
> Phone number :+39-0461-28-2414
> XRD lab:: +39-0461-282434
> Fax : +39-0461-28-1977
> 
> 
> 
>  
>  
> On 19 Dec 2016, at 18:23, Vogel, Sven C <s...@lanl.gov 
> <mailto:s...@lanl.gov>> wrote:
>  
> Hi Othman,
> 
> Another insightful thing to do might be to simulate diffraction patterns for 
> various scenarios. If you have B on two sites and simulate if the diffraction 
> pattern will look different for different occupancies on those two sites, 
> resulting in a given overall stoichiometry, you can convince yourself whether 
> diffraction is a good tool to determine SOFs. You can also check which 
> diffraction peaks show the biggest change, which may affect your count time 
> or region of interest. If you also simulate for neutrons and see a big change 
> for neutrons, but not X-rays, you have a good case to supplement a neutron 
> beam time proposal.
> 
> Good luck,
> 
> Sven
> 
> 
> 
> From: rietveld_l-requ...@ill.fr <mailto:rietveld_l-requ...@ill.fr> 
> [rietveld_l-requ...@ill.fr <mailto:rietveld_l-requ...@ill.fr>] on behalf of 
> Othman Al Bahri [z3435...@zmail.unsw.edu.au 
> <mailto:z3435...@zmail.unsw.edu.au>]
> Sent: Monday, December 19, 2016 1:54 AM
> To: rietveld_l@ill.fr <mailto:rietveld_l@ill.fr>
> Subject: Stoichiometry and occupancy fractions of solid solutions
> 
> Dear all,
>  
> I've made a series of solid solution powders using a solid state reaction in 
> the form A2B3-xCxO12 at x= 0.5 steps. A2B3O12 is orthorhombic while A2C3O12 
> is monoclinic. I'm refining the XRD data to find the atomic distribution of 
> the solute. 
>  
> I've constrained the sum of the occupancy fractions for each relevant site to 
> equal 1. At low concentrations of the solute, I initially set the solute's 
> occupancy fractions to 0 and keep the solvent's occupancy at 1 then refine 
> the fractions (after following the usual Rietveld refinement steps). This 
> seems to give reasonable occupancy fraction values (no big numbers or 
> negative values)

Re: Stoichiometry and occupancy fractions of solid solutions

[Luca Lutterotti]

To increase sensitivity to partial/mixed occupation and also solve the case of 
3 or more atoms in the same site (you have an infinite number of solutions that 
give you the same scattering factor, both x-ray and neutrons) we are developing 
a combined XRD-XRF analysis. Some preliminary application examples were 
published and we are preparing a full article on the theory behind.
https://www.researchgate.net/publication/288701415_Combined_X-Ray_diffraction_and_fluorescence_analysis_in_the_cultural_heritage_field
 
<https://www.researchgate.net/publication/288701415_Combined_X-Ray_diffraction_and_fluorescence_analysis_in_the_cultural_heritage_field>

Best regards,

Luca

---Luca 
Lutterotti
Dipartimento di Ingegneria Industriale, Universita' di Trento,
via Sommarive, 9, 38123 Trento, Italy

e-mail address : luca.luttero...@unitn.it <mailto:luca.luttero...@ing.unitn.it>
Maud page : http://maud.radiographema <http://maud.radiographema/>.com

Phone number :+39-0461-28-2414
XRD lab:: +39-0461-282434
Fax : +39-0461-28-1977




> On 19 Dec 2016, at 18:23, Vogel, Sven C <s...@lanl.gov> wrote:
> 
> Hi Othman,
> 
> Another insightful thing to do might be to simulate diffraction patterns for 
> various scenarios. If you have B on two sites and simulate if the diffraction 
> pattern will look different for different occupancies on those two sites, 
> resulting in a given overall stoichiometry, you can convince yourself whether 
> diffraction is a good tool to determine SOFs. You can also check which 
> diffraction peaks show the biggest change, which may affect your count time 
> or region of interest. If you also simulate for neutrons and see a big change 
> for neutrons, but not X-rays, you have a good case to supplement a neutron 
> beam time proposal.
> 
> Good luck,
> 
> Sven
> 
> 
> 
> From: rietveld_l-requ...@ill.fr [rietveld_l-requ...@ill.fr] on behalf of 
> Othman Al Bahri [z3435...@zmail.unsw.edu.au]
> Sent: Monday, December 19, 2016 1:54 AM
> To: rietveld_l@ill.fr
> Subject: Stoichiometry and occupancy fractions of solid solutions
> 
> Dear all,
> 
> I've made a series of solid solution powders using a solid state reaction in 
> the form A2B3-xCxO12 at x= 0.5 steps. A2B3O12 is orthorhombic while A2C3O12 
> is monoclinic. I'm refining the XRD data to find the atomic distribution of 
> the solute. 
> 
> I've constrained the sum of the occupancy fractions for each relevant site to 
> equal 1. At low concentrations of the solute, I initially set the solute's 
> occupancy fractions to 0 and keep the solvent's occupancy at 1 then refine 
> the fractions (after following the usual Rietveld refinement steps). This 
> seems to give reasonable occupancy fraction values (no big numbers or 
> negative values) but the stoichiometry is way off. This is probably because 
> each site has different Wykoff multiplicities so constraining the sum of each 
> site's fractions to 1 is insufficient.
> 
> Let's assume that I knew the stoichiometry from Mass Spectroscopy or XPS - is 
> there a way to constrain the stiochiometry in a Rietveld refinement? I'm 
> using GSAS-II and comfortable with FullProf but feel free to give advice for 
> any other open-source software.
> 
> I've seen a few papers where the authors mention, typically in the 
> supplementary info, that their refinements' stoichiometry was off and that it 
> should be ignored. However I'm not comfortable with this approach and would 
> appreciate your advice.
> 
> This is my first time working with solid solutions so please feel free to 
> offer any general advice on what I should be careful with. I've tested for 
> phase mixtures (insolubility) by visually comparing my XRD patterns with the 
> sum of simulated XRD patterns of molar mixtures and through Rietveld 
> refinements with two phases. The system I'm working with has been reported 
> but the original authors didn't do Rietveld refinements - they were 
> interested in physical property measurements.
> 
> Kind Regards,
> 
> Othman
> ++
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> Send commands to <lists...@ill.fr> eg: HELP as the subject with no body text
> The Rietveld_L list archive is on 
> http://www.mail-archive.com/rietveld_l@ill.fr/
> ++

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++

Re: TOPAS Macro Language (peak shape broadening macros)

[Luca Lutterotti]

 On 23 Jun 2015, at 22:22, Khalifah, Peter kp...@bnl.gov wrote:
 
 Preferred orientation results in the central assumption that the measured 
 intensity is proportional to the reflection structure being violated, 

This is actually quite new to me as definition of preferred orientation or 
better texture. Until now I thought that in the case of preferred orientations 
the measured intensity is proportional to the volume fraction of grains 
oriented in a certain direction…….

 As many people will tell you, it is much more effective to eliminate 
 preferred orientation (though improved sample preparation) than to try to 
 model it.  

We actually use preferred orientation (texture) to help structure solution, and 
I found more easy to model them than to eliminate them. But may be is just me.

Best regards,

Luca Lutterotti

---Luca 
Lutterotti
Dipartimento di Ingegneria Industriale, Universita' di Trento,
via Sommarive 9, 38123 Trento, Italy

Temporary address:
Laboratoire CRISMAT-ENSICAEN, Université de Caen Basse-Normandie, Campus 2
6, Bd. M. Juin 14050 Caen, France

e-mail address : luca.luttero...@unitn.it
Home page : http://www5.unitn.it/People/en/Web/Persona/PER0004735
New Maud page : http://maud.radiographema.com

Phone number :+39-0461-28-2414
Fax : +39-0461-28-1977--++
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++

Re: Anomalous scattering factor and Dispersion coefficients

[Luca Lutterotti]

John is correct, be careful that you are trying to compare same quantities but 
in a completely different units and definitions. I discover by myself that you 
cannot mix scattering factors, absorption factors, photo absorption etc. coming 
some from the diffraction community and some from the spectroscopic community. 
So Henke is used by the spectroscopic community (second link) and need proper 
conversion to be applied for scattering…..
I actually use Henke derived work in Maud now as I can compute the dispersion 
coefficients (and absorption) for every wavelength not only the tabulated ones 
usually adopted in diffraction, but I had to convert everything to be 
consistent (absorption etc.).

Best regards,

Luca
 
 On Jun 11, 2015, at 6:07 PM, Jonathan WRIGHT wri...@esrf.fr wrote:
 
 Dear Xiaodong, Jeremy,
 
 Isn't it equation 3 here?  
 http://www.nist.gov/srd/upload/jpcrd488.pdf 
 http://www.nist.gov/srd/upload/jpcrd488.pdf
 f1/f2 are dispersion numbers and f'/f are the anomalous ones. The 
 relativisitic correction number for iron then shows up on page 221. 
 
 Best,
 
 Jon
 ===
 
 On 11/06/2015 17:27, Jeremy Karl Cockcroft wrote:
 Hi Xiaodong,
 I think that the numbers quoted for f' in the second case have had 26e 
 (atomic no.) added to them, i.e. it refers to the total dispersion value for 
 the real component (as opposed to the imaginary component). Given that the 
 numbers quoted are close to an absorption edge, then the remaining 
 differences are not unexpected depending on source and precise energy 
 quoted. If graphs of the data are plotted with Z subtracted, then they look 
 very similar apart from the precise value of the minimum of f' at the 
 absorption edge itself.
 Just my thoughts on it... 
 Jeremy Karl.
 ***
 Dr Jeremy Karl Cockcroft
 Department of Chemistry
 (University College London)
 Christopher Ingold Laboratories
 20 Gordon Street
 London WC1H 0AJ
 United Kingdom
 +44 (0) 20 7679 1004 (laboratory)
 j.k.cockcr...@ucl.ac.uk mailto:j.k.cockcr...@ucl.ac.uk or 
 jeremyk...@gmail.com mailto:jeremyk...@gmail.com
 http://img.chem.ucl.ac.uk/www/cockcroft/homepage.htm 
 http://img.chem.ucl.ac.uk/www/cockcroft/homepage.htm
 ***
 
 
 On 11 June 2015 at 15:33, iangie ian...@126.com mailto:ian...@126.com 
 wrote:
 Dear Rietvelders,
 
 I am little confused about the term Anomalous scattering factor and 
 Dispersion coefficients.
 Anomalous scattering factor can be found here 
 http://skuld.bmsc.washington.edu/scatter/AS_form.html 
 http://skuld.bmsc.washington.edu/scatter/AS_form.html
 Dispersion coefficients can be found here 
 http://www.cxro.lbl.gov/optical_constants/asf.html 
 http://www.cxro.lbl.gov/optical_constants/asf.html 
 
 Their numbers are quite different: e.g. Fe @ CrKα: f0=18.474, Δf'=-1.6 
 Δf=0.9 ;however, the corresponding dispersion coefficients are f' 
 ~24.6808 and f ~0.759346
 Can anyone explain their relationship?
 
 Thanks!
 --
 Yours Sincerely,
 Dr. Xiaodong(Tony) Wang
 XRD Application Scientist
 Bruker Singapore Pte. Ltd.
 
 ++
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 ++
 
 
 
 
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 ++
 

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++

Re: Stacking faults and antiphase boundary

[Luca Lutterotti]

Sorry Leonid,

but here we are talking about densities of stacking faults around 1% (that
is anyway quite a high value for these alloys). Your quantification was
less than that. Now it means you have one cell every 100 affected for the
intensities. How much change do you expect to have?
Your occupancy of the 0,0,1/3 is way higher than that (nearly 1/3 if I
remember). Then you have the B factor trying to compensating the wrong
intensities given by this too high occupation. But it alters even more the
quantification.
Now, this sample come from a rapidly solidified ribbon. There you have
only a B2 homogeneous phase, but by thermal treatment we get the
equilibrium phases in agreement with the phase diagram (alpha phase about
1/3 weight or volume). We ball milled some of them at different time, all
of them stay close to the 1/3 and the 48 hours ball milled showed quite a
bit more going closer to 1/2 (but if you anneal again you get 1/3). The
1/2 it is already a bit stretched and meaning we are not in equilibrium
with the Cu-Zn composition for the two phases.
But now in your analysis you get 2/3 which is practically impossible from
the material/alloy point of view. So there should be a problem somewhere
right?
Cu and Zn have only one electron difference, so in X-ray even using full
Zn or Cu does not affect the intensities, but your 0,0,1/3 occupation it
does when you go to values over 0.1 (10%) that is not feasible in such
alloy.

Best regards,

Luca


 Dear Luca,


 Now I see the principal problem of your faulting model. You do not take
 into account the influence of faults on the peak INTENSITIES, which is
 definitely wrong. This explains the discrepancies in the QPA results and
 Biso.
 In the faulted crystal some layers of atoms are displaced from the ideal
 sites of the cubic close-packed lattice. These displacements give rise to
 both the peak broadening and the intensity alterations. In my model I take
 it into account by the inclusion of the additional atomic pseudo-position.
 In your model you use an idealized cubic FCC structure and, thus,
 idealized intensities which differ from the real ones due to the faulting.
 So, my quantification should not go closer to yours.

  
 Best regards,

 Leonid

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


 - Original Message -
 From: Luca Lutterotti luca.luttero...@ensicaen.fr
 To: Leonid Solovyov l_solov...@yahoo.com
 Cc:
 Sent: Thursday, April 3, 2014 6:33 PM
 Subject: Re: Stacking faults and antiphase boundary

 Dear Leonid,

 if you wish to know, using the trigonal space group and populating the
 0,0,1/3 site (even keeping the same number of atoms in the cell) it
 affects the intensities. Try yourself by simulation with low broadening to
 see it better. This is what make your quantification wrong. You can try as
 a counterexample to fit the bbm48bis using the FCC model. Do not care if
 the two first peaks are displaced, focus on the intensities. You
 quantification will go closer to mine.

 Best regards,

     Luca


 On Apr 3, 2014, at 7:16, Leonid Solovyov l_solov...@yahoo.com wrote:

 Dear Luca,

 I'm glad to see your interest to the problem even after such a delay.

 So in the end, your model for faulting as you describe:
 A more general model [J Appl Cryst (2000) 338] is included in DDM:
 was to use a trigonal
 cell with hexagonal axis to allow refining the anisotropic shift of the
 peaks caused by the planar defects? That is a nice trick, you can try
 to
 justify it by reasoning that one effect of the planar defect is to get
 same stacking sequence of the hexagonal (we all know that), but what
 about
 the FCC stacking now?

 I chose the trigonal setting since the presence of layered faults
 decreases the symmetry of the
 material making it intermediate between cubic close-packed and hexagonal
 close-packed. This is
 an approximation of the real complex structure, of course, but I find it
 applicable to most cases
 of close-packed faulted materials I've dealt with. In some cases one has
 to choose more
 sophisticated models in order to account for peculiar diffraction
 features due to correlations
 between faults, see, for instance Fig. 2 in [O. Ersen, J. Parmentier, L.
 A. Solovyov, M. Drillon,
 C. Pham-Huu, J. Werckmann, P. Schultz, Direct Observation of Stacking
 Faults and Pore
 Connections in Ordered Cage-Type Mesoporous Silica FDU-12 by Electron
 Tomography.
 J. Am. Chem. Soc. (2008) 16800]

 To make the audience aware, just changing the cell was not sufficient,
 you
 have to reproduce the intensities. So in the structure a couple of Cu,
 Zn
 was set in 0,0,0 and another in 0,0,1/3 and the occupancies refined (to
 values as 1.10392 for the first position and 0.39608 for the second,
 but
 look like the second

Re: Stacking faults and antiphase boundary

[Luca Lutterotti]

but here we are talking about densities of stacking faults around 1%
(thatis anyway quite a high value for these alloys).
Your quantification was less than that. Now it means you have one cell
every 100 affected for the intensities. How much change do you expect to
have? Your occupancy of the 0,0,1/3 is way higher than that (nearly 1/3
if Iremember). Then you have the B factor trying to compensating the
wrong intensities given by this too high occupation. But it alters even
more the quantification.

 In the DDM-input file the column N contains N of atoms per unit cell,
not the occupancy. This is written in the manual. So, the total
occupancy of the additional (0,0,1/3) position (by Zn + Cu) is around
0.13, which is high enough to notably affect the intensities. If you
don’t take this effect into account you have biased results.

In fact as I said, this is the problem, it should not, given the low
density of such defects. But I see you are not willing to revise
critically your model. So the discussion will go nowhere and will actually
a bit boring for the other, so for my part it end here. If you wish to
really check the model, I am available in private by email.


 Regarding the sample, I’m not ready to discuss its properties here as
I did not work with it.

Well, this is not my way to work. When the results are against the
physical laws I am always trying to find the reason. We can make easily
errors (more than nature).

Best regards,

Luca


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

  

 - Original Message -
 From: Luca Lutterotti luca.luttero...@ing.unitn.it
 To: Leonid Solovyov l_solov...@yahoo.com
 Cc: Luca Lutterotti luca.luttero...@ensicaen.fr; rietveld_l@ill.fr
rietveld_l@ill.fr
 Sent: Friday, April 4, 2014 1:20 PM
 Subject: Re: Stacking faults and antiphase boundary

 Sorry Leonid,

 but here we are talking about densities of stacking faults around 1%
(that is anyway quite a high value for these alloys). Your
quantification was less than that. Now it means you have one cell every
100 affected for the intensities. How much change do you expect to have?
 Your occupancy of the 0,0,1/3 is way higher than that (nearly 1/3 if I
remember). Then you have the B factor trying to compensating the wrong
intensities given by this too high occupation. But it alters even more
the quantification.
 Now, this sample come from a rapidly solidified ribbon. There you have
only a B2 homogeneous phase, but by thermal treatment we get the
equilibrium phases in agreement with the phase diagram (alpha phase
about 1/3 weight or volume). We ball milled some of them at different
time, all of them stay close to the 1/3 and the 48 hours ball milled
showed quite a bit more going closer to 1/2 (but if you anneal again you
get 1/3). The 1/2 it is already a bit stretched and meaning we are not
in equilibrium with the Cu-Zn composition for the two phases.
 But now in your analysis you get 2/3 which is practically impossible
from the material/alloy point of view. So there should be a problem
somewhere right?
 Cu and Zn have only one electron difference, so in X-ray even using full
Zn or Cu does not affect the intensities, but your 0,0,1/3 occupation it
does when you go to values over 0.1 (10%) that is not feasible in such
alloy.

 Best regards,

 Luca



 Dear Luca,


 Now I see the principal problem of your faulting model. You do not take
into account the influence of faults on the peak INTENSITIES, which is
definitely wrong. This explains the discrepancies in the QPA results
and Biso.
 In the faulted crystal some layers of atoms are displaced from the
ideal sites of the cubic close-packed lattice. These displacements give
rise to
 both the peak broadening and the intensity alterations. In my model I take
 it into account by the inclusion of the additional atomic
 pseudo-position.
 In your model you use an idealized cubic FCC structure and, thus,
idealized intensities which differ from the real ones due to the
faulting.
 So, my quantification should not go closer to yours.

  
 Best regards,

 Leonid

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


 - Original Message -
 From: Luca Lutterotti luca.luttero...@ensicaen.fr
 To: Leonid Solovyov l_solov...@yahoo.com
 Cc:
 Sent: Thursday, April 3, 2014 6:33 PM
 Subject: Re: Stacking faults and antiphase boundary

 Dear Leonid,

 if you wish to know, using the trigonal space group and populating the
0,0,1/3 site (even keeping the same number of atoms in the cell) it
affects the intensities. Try yourself

[no subject]

[Luca Lutterotti]

Dear Leonid,

On Apr 3, 2014, at 7:16, Leonid Solovyov l_solov...@yahoo.com wrote:

Dear Luca,

I'm glad to see your interest to the problem even after such a delay.

So in the end, your model for faulting as you describe:
A more general model [J Appl Cryst (2000) 338] is included in DDM: was
to use a trigonal
cell with hexagonal axis to allow refining the anisotropic shift of the
peaks caused by the planar defects? That is a nice trick, you can try to
justify it by reasoning that one effect of the planar defect is to get
same stacking sequence of the hexagonal (we all know that), but what about
the FCC stacking now?

I chose the trigonal setting since the presence of layered faults
decreases the symmetry of the
material making it intermediate between cubic close-packed and hexagonal
close-packed. This is
an approximation of the real complex structure, of course, but I find it
applicable to most cases
of close-packed faulted materials I've dealt with. In some cases one has
to choose more
sophisticated models in order to account for peculiar diffraction
features due to correlations
between faults, see, for instance Fig. 2 in [O. Ersen, J. Parmentier, L.
A. Solovyov, M. Drillon,
C. Pham-Huu, J. Werckmann, P. Schultz, Direct Observation of Stacking
Faults and Pore
Connections in Ordered Cage-Type Mesoporous Silica FDU-12 by Electron
Tomography.
J. Am. Chem. Soc. (2008) 16800]

It is what I anticipated in my message, finally you admit you use an
approximation; in Maud I use instead the real complex structure, so the
FCC with the planar defects, all of three types as they cause different
modifications to the pattern, and I obtain the density of each one. So I
don't see any advancement in your approach to justify your initial claim
of a better model.


To make the audience aware, just changing the cell was not sufficient, you
have to reproduce the intensities. So in the structure a couple of Cu, Zn
was set in 0,0,0 and another in 0,0,1/3 and the occupancies refined (to
values as 1.10392 for the first position and 0.39608 for the second, but
look like the second is calculated from the first) to adjust the
intensities and the density.

Yes, the additional (0,0,1/3) position is included in the model to
account for the partial
displacement of atoms from ideal CCP sites due to the faulting. It allows
accounting for the
influence of faults on both the intensities and the peak broadening
according to the methodology
described in J Appl Cryst (2000) 338.

But actually this didn't work out completely
as the resulting quantitative phase analysis is completely wrong.

Why do you think that the QPA is wrong? Just because it differs from what
you have from
Maud???

No, because I made the sample, this is only one of a serie, and I analysed
it years ago not with Maud, even before I started writing Maud, I analysed
also it by neutrons and I know it very well.
You should do some test and verify that when you use a model not based on
the correct crystallographic setting, it is not assured that the total
scattering will keep its intensity (there is an old paper of Warren, if I
remember well was by him about it, I will try to find it). It means that
it will affect your scale factor and in the end your volumetric quantity.
Not to mention again that the B factor for your alpha approximation is
completely wrong. This also affect your results.


And where are the crystallite sizes? Planar defect densities? So what kind
of results did you get from the material science point of view?

I can't determine the crystallite size from this pattern since I don't
have the instrumental
broadening information. As for the faulting probability, it can be
derived form eq. 5 of J Appl
Cryst (2000) 338. For the alpha-brass phase, the fraction C of defective
cells (atoms displaced by
faults) is given by the total occupancy of the pseudo-position at
(0,0,1/3) that is refined to 0.132.
The reciprocal values (1/t1 - 1/t) are listed in the column hkl of the
DDM-output reflections
listing. For the faulting direction [003] this value is 64.2A. Thus, the
fault probability:
p = 2Cd(001)(1/t1 - 1/t) = 2*0.132*2.1464/64.2 = 0.0088
This value, however, may be biased as I don't have the instrumental
broadening parameters.

The instrumental broadening was in the Maud analysis and parameter file
you used. You could have used it.
Then you get one planar defect quantity representing both the two type of
deformation faulting (slip) and twin. How you can mix twin and slip if
hard to me to understand.

I
must also note that for such low-quality data one can hardly expect
highly-reliable
microstructural characteristics.

Well, in Maud i can, it is sufficient using the correct model. But it is
not you who claim that the ddm model can do anything and magically get
quantities out of nothing or I misunderstood your discussion with Armel?

You have to relax a bit, the ddm is an interesting approach. I personally
think is an improvement when dealing with medium/high crystallised

Re: Stacking faults and antiphase boundary

[Luca Lutterotti]

Dear Leonid,

sorry to come back to an old thread, but there is something to be know
that you didn't tell completely.
So finally I came across this morning to a picture of the fit by ddm of
this bbm48bis sample with planar defects (coming from Maud examples,
picture and example now also on the ddm web site). I didn't see it at that
time as it was not included in the zip of Leonid and I didn't have Windows
to install ddm and check it (nor the time).
Now that I saw in the picture that Leonid did not use a cubic cell to fit
the alpha-brass, I took the time to download ddm, and check the solution.

So in the end, your model for faulting as you describe: A more general
model [J Appl Cryst (2000) 338] is included in DDM: was to use a trigonal
cell with hexagonal axis to allow refining the anisotropic shift of the
peaks caused by the planar defects? That is a nice trick, you can try to
justify it by reasoning that one effect of the planar defect is to get
same stacking sequence of the hexagonal (we all know that), but what about
the FCC stacking now?
To make the audience aware, just changing the cell was not sufficient, you
have to reproduce the intensities. So in the structure a couple of Cu, Zn
was set in 0,0,0 and another in 0,0,1/3 and the occupancies refined (to
values as 1.10392 for the first position and 0.39608 for the second, but
look like the second is calculated from the first) to adjust the
intensities and the density. But actually this didn't work out completely
as the resulting quantitative phase analysis is completely wrong. Not to
mention a quite high B factor (2.17 compared to the near 0.6 value of Maud
and the other BCC phase) for the atoms in the alpha phase, probably to
compensate for the wrong structure and kill the two high peaks at high
angle resulting from the trigonal structure.

Well this kind of trick may be able in certain cases to fit the pattern
(here just because peaks are broad and you don't notice the split on the
first peak and others of the alpha), but the results you get speak for
themselves.
And where are the crystallite sizes? Planar defect densities? So what kind
of results did you get from the material science point of view?
You could have used just a full profile pattern fitting at this point, and
at least get the crystallite sizes. So now I am asking myself why I don't
use always a triclinic cell to describe my phases, I will have the
flexibility to fit everything without resorting to complex physical
models.

Best regards,

Luca

On Jun 28, 2013, at 6:34, Leonid Solovyov l_solov...@yahoo.com wrote:

Dear Luca,

My doubts regarding the applicability of the faulting model in Moud are
due to the absence of its description in the program and the
non-availability of options required for crystal systems where the faulted
atomic displacements and domain planes are not obviously pre-defined as in
the close-packed metals.
The model included in DDM is, indeed, simplified and phenomenological to
some extent (as well any other model) but it is equally applicable to any
structure with any crystallographic symmetry and any faulting type that
may be described by a lattice of unit cell domains differing in the atomic
arrangement. For your bbm48bis example it gives a similar profile fit as
that in Maud in both Rietveld and DDM mode with even fewer number of
variable parameters - 14 for DDM and 17 for Rietveld compared to 22 in
Maud:
http://sites.google.com/site/ddmsuite/tutorials/bbm48bis.zip
The profile R-factor output by DDM in the Rietveld mode is high (20.77%)
since it is calculated for the background-subtracted data. The equivalent
“standard” Rwp is 7.88% (and 7.59% in Maud). Some microstructural variable
parameters in the Maud model bbm48bis.par are, apparently, excessive as
their estimated errors exceed the refined values.
Concerning the FeAl.ddm example, it does contain antiphase domains whose
influence on the selective broadening is allowed for by the connection
between the pseudo-position occupancy and the size-ellipsoid (regulated by
the NDPAR field).

Best regards,
Leonid
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***
From: Luca Lutterotti luca.luttero...@ing.unitn.it
To: rietveld_l@ill.fr rietveld_l@ill.fr
Sent: Wednesday, June 26, 2013 5:19 PM
Subject: Re: Stacking faults and antiphase boundary

I made a quick analysis on Leonid FeAl example.
Very simple, no stacking/twin faults, no antiphase domains, only
stoichiometry is 15% in favor of Fe. So you only fit the relative
occupancy of Al and the different sites accordingly.
So if you want to compare the two programs on that simple example, you can
download:
http://www.ing.unitn.it/~maud/FeAl.zip

there are the same files of the example of Leonid, plus I added:
FeAl_m.dat  (reformatted data file

Re: Preferred orientation?

[Luca Lutterotti]

On May 8, 2008, at 12:30 AM, May, Frank wrote:

You can check for texture effects (preferred orientation) by  
obtaining multiple patterns of the material.  It's realistic to  
expect some differences, but preferred orientation is manifest by  
not being able to replicate the pattern.



Not true,

preferred orientation or texture are perfectly reproducible, provided  
you use the same sample orientation. What is not reproducible and  
probably what Frank May is referring to is not preferred orientation  
but graininess or few big grains that do not guarantee the correct  
statistic. So if you need to check for graininess, you just move a  
little your sample, so the beam covers a different area on the sample.  
If you think you have texturte, to check for it you have to change the  
sample orientation to see a change. Beware that in a Bragg-Brentano  
instrument turning around the axis normal to the sample surface is not  
a valid change in orientation as nothing will change for texture; you  
have to change the sample inclination instead (omega or chi).


Best Regards,

Luca Lutterotti





That's the simple test.  Let us know what you find.

Another issue for improper intensities is when the specimen is not  
sufficiently wide enough at low angles (typically below 20-degrees 2- 
Theta with copper radiation) and the x-ray beam does not fully  
impinge on the specimen.  The observed reflections in the low angle  
region will be less than calculated by a modelling program.


Frank May
Research Investigator
Department of Chemistry and Biochemistry
University of Missouri - St. Louis
One University Boulevard
St. Louis, Missouri  63121-4499

314-516-5098



From: Gerard, Garcia S [mailto:[EMAIL PROTECTED]
Sent: Wed 5/7/2008 8:57 AM
To: rietveld_l@ill.fr
Subject: Preferred orientation?



Dear all,

I have a laboratory Bragg-Brentano X-ray (Cu) pattern that shows  
intensity mismatches only at low angles, ie 20-50 2theta or 1.8 to 4  
Angstroms.
There are overestimated peaks and also underestimated peaks.I have  
tried to discard factors that might cause this problem:


The thermal parameters look sensible. Moreover, the data at high  
angle looks ok, so intensity transfer from low angle to high angle  
or vice versa does not seem to be the cause.


Atomic positions also look sensible. And again, data at high angle  
looks ok. Is the scattering angle dependence of the atomic positions  
the same as for the thermal parameters? (I cannot remember that, but  
i am pretty sure it is not).


Following the advice published in J. Appl. Cryst. 32, 36 (1999), the  
other factor that might cause this problem is preferred orientation:
I have tried to find a hkl dependence in the overestimated and  
underestimated peaks but i could not find any. If i try to model  
preferred orientation with spherical harmonics the problems  
disappears nicely. The problem is how to justify the existence of  
preferred orientation. The crystal system is orthorhombic. But i  
have no other information that supports the existence of preferred  
orientation.


Is there any other problem that I cannot think of?Is the preferred  
orientation correction masking any of these other problems I cannot  
think of?


Regards

Gerard





Heriot-Watt University is a Scottish charity registered under  
charity number SC000278.

Re: Preferred orientation?

[Luca Lutterotti]

Reinhard,

I stick with what Gerard said:

But i have no other information that supports the existence of  
preferred orientation


so what information give you the confirmation it is the powder mount  
responsible of preferred orientation. I work almost exclusively with  
image plate detectors and I can assure you that the graininess problem  
is appearing more often than the preferred orientation case. I am  
working on texture mostly so I am happy when you find them, but this  
case is not s frequent as people think and for sure not s frequent as  
graininess.


I wait also confirmation from Gerard that his sample is a powder and  
it has plate like or fiber like particles. Otherwise I will  
investigate the graininess case that with a proper grinding or a  
spinner is easily resolvable.


Also, for who think that because the harmonic model can fit it is for  
sure preferred orientation. I can just suggest to work for a while  
with real textured sample and the harmonic and see if there is really  
this relationship, you may be surprise by the result.


cheers,
Luca

On May 8, 2008, at 3:08 PM, Reinhard Kleeberg wrote:


Luca,
speaking about powder samples, Frank is right. The PO of powder  
mounts is seldom reproducible and the filling technique is  
responsible for particle orientation, depending on particle shape,  
filling direction, pressure... In practice it is a nice trick to  
repeat the filling of the powder holder with different filling  
techniques to look for PO. Of course, sample graininess may be also  
a reason for not reproducible intensity, but these effects (rocks  
in the dust) ar mostly hard to correct successfully by spherical  
harmonics as Gerard stated for his problem. In any case, the problem  
sounds to be related to sample preparation.

Reinhard

Luca Lutterotti schrieb:


On May 8, 2008, at 12:30 AM, May, Frank wrote:

You can check for texture effects (preferred orientation) by   
obtaining multiple patterns of the material.  It's realistic to   
expect some differences, but preferred orientation is manifest by   
not being able to replicate the pattern.




Not true,

preferred orientation or texture are perfectly reproducible,  
provided  you use the same sample orientation. What is not  
reproducible and  probably what Frank May is referring to is not  
preferred orientation  but graininess or few big grains that do not  
guarantee the correct  statistic. So if you need to check for  
graininess, you just move a  little your sample, so the beam covers  
a different area on the sample.  If you think you have texturte, to  
check for it you have to change the  sample orientation to see a  
change. Beware that in a Bragg-Brentano  instrument turning around  
the axis normal to the sample surface is not  a valid change in  
orientation as nothing will change for texture; you  have to change  
the sample inclination instead (omega or chi).


   Best Regards,

   Luca Lutterotti





That's the simple test.  Let us know what you find.

Another issue for improper intensities is when the specimen is  
not  sufficiently wide enough at low angles (typically below 20- 
degrees 2- Theta with copper radiation) and the x-ray beam does  
not fully  impinge on the specimen.  The observed reflections in  
the low angle  region will be less than calculated by a modelling  
program.


Frank May
Research Investigator
Department of Chemistry and Biochemistry
University of Missouri - St. Louis
One University Boulevard
St. Louis, Missouri  63121-4499

314-516-5098



From: Gerard, Garcia S [mailto:[EMAIL PROTECTED]
Sent: Wed 5/7/2008 8:57 AM
To: rietveld_l@ill.fr
Subject: Preferred orientation?



Dear all,

I have a laboratory Bragg-Brentano X-ray (Cu) pattern that shows   
intensity mismatches only at low angles, ie 20-50 2theta or 1.8 to  
4  Angstroms.
There are overestimated peaks and also underestimated peaks.I  
have  tried to discard factors that might cause this problem:


The thermal parameters look sensible. Moreover, the data at high   
angle looks ok, so intensity transfer from low angle to high  
angle  or vice versa does not seem to be the cause.


Atomic positions also look sensible. And again, data at high  
angle  looks ok. Is the scattering angle dependence of the atomic  
positions  the same as for the thermal parameters? (I cannot  
remember that, but  i am pretty sure it is not).


Following the advice published in J. Appl. Cryst. 32, 36 (1999),  
the  other factor that might cause this problem is preferred  
orientation:
I have tried to find a hkl dependence in the overestimated and   
underestimated peaks but i could not find any. If i try to model   
preferred orientation with spherical harmonics the problems   
disappears nicely. The problem is how to justify the existence of   
preferred orientation. The crystal system is orthorhombic. But i   
have no other information that supports the existence of  
preferred

Re: wt% to volume percent

[Luca Lutterotti]

Dear Tony,

diffraction intensity are sensible to volume fractions, not weight  
percent. What you see in the Rietveld formulas are weight fractions  
because they convert the scale parameter (in which there is the  
volume fraction) into weight fractions using the density (the ZMV  
factor containing number of molecules, molecular weight and cell  
volume, a way to get the density taking into account the scale factor  
contains also a squared cell volume at the denominator).


So to get volume fraction it's more easy as you only do:

vol % phase i = (scale factor phase i) / Sum(all phases scale factors)

no density involved.

Best regards,

Luca Lutterotti

On Mar 10, 2007, at 11:52 PM, Mr. Tony Raftery wrote:


Guys,

can anyone send me description (or reference) for the conversion of  
weight percent to volume percent for a (solid) mixture - volume  
percent is favored by metallurgists (and others).


thanks in advance,

Tony Raftery
Tony Raftery
Senior Technologist
AEMF  XAF, R Block
Faculty of Science, GP
Queensland University of Technology
c/- AEMF, R Block
Gardens Point Road, Brisbane, 4000 (or)
GPO Box 2434
Brisbane  4001 AUSTRALIA

ph  +61 7 3138 2271
fax +61 7 3138 5100
email   [EMAIL PROTECTED]
http://www.xaf.qut.edu.au/

please note new phone number from 16/10/2006

Re: Embedded plots, was Re: Powder Diffraction In Q-Space

[Luca Lutterotti]

On Feb 22, 2007, at 2:20 PM, Jonathan Wright wrote:


From http://www.iucr.org/iucr-top/cif/faq/


# What is DDL3?

DDL version 3 is the name given to some work in progress by Syd  
Hall and his colleagues at the University of Western Australia. It  
is intended to build on the greater consistency and data typing  
abilities of DDL2 without tying the data model too closely to that  
of a relational database. A particular goal of DDL3 is to  
introduce methods into data dictionaries through a formal language  
known as dREL (Dictionary Regular Expression Language).


I've not seen a DDL3 example, but many cases can probably be  
covered with what is in pdCIF already.


The application which does the plotting doesn't need to end up  
inside the cif as part of the file, but the equation linking  
detector pixels to Q could be very useful. There has been a good  
deal of effort already in ImageCIF for single crystal experimental  
data.


I understood Maud can read and plot cifs already, and is written in  
Java? Could there be a browser plugin version for this?




Correct, it read data (datafiles and structures) in CIF format. It  
use the CIF sintax also for saving its own analysis files (with the  
addition of some extra non cif definitions missing in the formal cif  
but needed by the program and extra file substructures embedded as  
comments).


In the past there was a browser/java applet version of Maud as well  
as a subsequent java webstart version, both are still in there and  
with the successive modifications I tried to keep the program  
compliant with them, with the idea to be able to activate them if  
needed. Only I have not used both of them recently so the first  
programmer rule states that what has not been tested does not work  
for sure.
But with a little work a java applet can be put again to work  
especially with the specific purpose of plotting CIF datafiles.


Well, in case someone is interested on it, he can just contact me  
with the idea/project and I may try to find out some spare time to do  
it. But I would prefer to have in case some specifications, files and  
what we need to just finalize and optimize it in the shortest time as  
possible.


Best regards,

Luca Lutterotti


Best,

Jon


On Thu, 22 Feb 2007, Alan Hewat wrote:


Now this sounds interesting. Certainly the raw data should be  
archived
and people could then plot it as they wish. But are there examples  
of interactive plotting applications embedded in powderCIF files,  
and what language might they use ? I would like to see a profile  
plotting package in Java or some other really portable language  
that would read in CIF files and plot calculated-observed patterns  
like Jmol now plots structures.

Alan.

_
Dr Alan Hewat, ILL Grenoble, FRANCE[EMAIL PROTECTED]fax+33.476.20.76.48
+33.476.20.72.13 (.26 Mme Guillermet)  http://www.ill.fr/dif/ 
people/hewat/

_

Re: Powder Diffraction In Q-Space

[Luca Lutterotti]

As we talk about plotting in Q-space (just for information in Maud is  
available from few months thanks to Klaus-Dieter advocating for it),  
I would advocate another plot option that I would rather see as a  
default way of plotting.


Looking at the other axis (the intensity) I am asking why we don't  
introduce the practice to plot in a more useful scale as the root  
square of the intensity (instead of the usual linear scale). This has  
several benefits:
- the plot will be at iso-error (I recall for who may have forgotten  
the noise is proportional to the root square of the intensity), so in  
the residuals you may better evaluate which are the peaks or part  
well fitted or poor fitted. Otherwise with the linear scale you just  
see only the bad residuals of the more intense peaks and you may  
think these are the peaks poorly fitted. Instead most of the time in  
the true statistical meaning they may be well fitted compare to  
other. In the square root intensity mode you can evaluate them more  
unbiased
- you see also the small peaks and it is not necessary to enlarge the  
intensity scale to check them


In this regard some people are using the log10 scale plot (normally  
used for reflectivity measurements). It may enhance more the small  
peaks but I don't favor it as again you do not compare the fitting of  
different peak on an equal statistical base.


As an image is better than thousand words, as they say, I put  
together one web page with the comparison of linear/sqrt/log10 scale,  
Q and 2theta so everyone may take its own conclusion.


http://www.ing.unitn.it/~maud/plotoptions/

I would encourage the list to propose a standard way (or advised way)  
to plot, as it would be not too difficult for the different program  
to provide a standard way to present the results for the benefit of  
comparisons.



Best regards,

Luca Lutterotti

Re: Powder Diffraction In Q-Space

[Luca Lutterotti]

Alan,

if it is trivial to plot in the square root I presume it is already  
available in Topas as well GSAS and Fullprof just to mention few. And  
if it is so trivial and already available as a button options why no  
one is using it. Why every time I look at a paper with a Rietveld  
refinement I can only appreciate the big peaks and why the residuals  
are so little meaningful at end? Every one can choose what he prefers  
obviously, but why all (without exceptions) are using not exactly the  
best way to just do a plot? Should not be trivial?


Conversion from 2theta - d -1/d is trivial in MY OPINION. This is  
really a problem of the programmer not of the users (in a Rietveld  
list). Constant step or variable step? Why it should influence the  
conversion except for the speed of the conversion. I am using fast  
fourier transform in my program for computing peak profiles directly  
from distribution of crystallites and microstrain; I don't assume any  
constant step, but seems like I can do it.


And this step or FT has really nothing to do with the original post  
of Klaus-Dieter who was focusing on just asking people if we can try  
to get used to a common way to plot data different from the  
conventional one. There are obviously favorable points and cons. Why  
we cannot discuss it. Seems like for the Rietveld users is not so  
trivial.


Oh, and no one is setting up web sites just to show  
opinions.may be these were already there...


Cheers,
Luca

On Feb 21, 2007, at 8:11 PM, AlanCoelho wrote:



Whether a program has a button to display data as a function of 1/d  
or a
button to take the square toor of intensities is trivial to the  
point of not

being talked about much less setting up web sites to get opinions.

The only point worth talking about is how a conversion from 2Th to  
1/d is

done in regards to takeing the fourier transform of a powder pattern.

alan


-Original Message-
From: Joerg Bergmann [mailto:[EMAIL PROTECTED]
Sent: Thursday, 22 February 2007 4:30 AM
To: rietveld_l@ill.fr
Subject: Re: Powder Diffraction In Q-Space

It's a principle of software design not to presume any kind of
equidistant data. Unfortunately, file formats for non-equidistant
data are seldom. So I could not implement any in BGMN, until now.
But, in principle, there is no restriction.

Regards

Joerg Bergmann

Re: Powder Diffraction In Q-Space

[Luca Lutterotti]

Bob,

for the negative points in case of a background subtraction I do a  
little trick. If the resulting data is negative I do the square root  
of the absolute value and I multiply by -1 (I retain the sign). So it  
plots in sqrt but remains negative.


Luca


On Feb 21, 2007, at 10:14 PM, Von Dreele, Robert B. wrote:

Actually, I looked at Luca's little show  was sufficiently  
interested

that GSAS will now plot sqrt(I) style plots. There is one problem -
the value of I can be negative particularly after a background
subtraction. These must be suppressed to zero for this plot to work -
thus there is a small risk of something getting hidden. Anyway -  
the new
version will be out in a day or two (after I make sure there are no  
bugs

introduced by this!)

R.B. Von Dreele
IPNS Division
Argonne National Laboratory
Argonne, IL 60439-4814



-Original Message-
From: Luca Lutterotti [mailto:[EMAIL PROTECTED]
Sent: Wednesday, February 21, 2007 2:59 PM
To: rietveld_l@ill.fr
Subject: Re: Powder Diffraction In Q-Space


Alan,

if it is trivial to plot in the square root I presume it is already
available in Topas as well GSAS and Fullprof just to mention few. And
if it is so trivial and already available as a button options why no
one is using it. Why every time I look at a paper with a Rietveld
refinement I can only appreciate the big peaks and why the residuals
are so little meaningful at end? Every one can choose what he prefers
obviously, but why all (without exceptions) are using not exactly the
best way to just do a plot? Should not be trivial?

Conversion from 2theta - d -1/d is trivial in MY OPINION. This is
really a problem of the programmer not of the users (in a Rietveld
list). Constant step or variable step? Why it should influence the
conversion except for the speed of the conversion. I am using fast
fourier transform in my program for computing peak profiles directly
from distribution of crystallites and microstrain; I don't assume any
constant step, but seems like I can do it.

And this step or FT has really nothing to do with the original post
of Klaus-Dieter who was focusing on just asking people if we can try
to get used to a common way to plot data different from the
conventional one. There are obviously favorable points and cons. Why
we cannot discuss it. Seems like for the Rietveld users is not so
trivial.

Oh, and no one is setting up web sites just to show
opinions.may be these were already there...

Cheers,
Luca

On Feb 21, 2007, at 8:11 PM, AlanCoelho wrote:



Whether a program has a button to display data as a function of 1/d
or a
button to take the square toor of intensities is trivial to the
point of not
being talked about much less setting up web sites to get opinions.

The only point worth talking about is how a conversion from 2Th to
1/d is
done in regards to takeing the fourier transform of a powder pattern.

alan


-Original Message-
From: Joerg Bergmann [mailto:[EMAIL PROTECTED]
Sent: Thursday, 22 February 2007 4:30 AM
To: rietveld_l@ill.fr
Subject: Re: Powder Diffraction In Q-Space

It's a principle of software design not to presume any kind of
equidistant data. Unfortunately, file formats for non-equidistant  
data



are seldom. So I could not implement any in BGMN, until now. But, in
principle, there is no restriction.

Regards

Joerg Bergmann

Re: stresses-crystal structure changes

[Luca Lutterotti]

Because you are collecting just in Bragg-Brentano condition, or if  
not for every collection you just see only one direction in the  
sample, not all together. And if you homogenize all together you will  
only observe a broadening of the peaks.


Best regards,

Luca Lutterotti

On Jan 20, 2007, at 8:02 PM, [EMAIL PROTECTED] wrote:


Dear all:

Let me make you the following question.

Suppose a polycrystalline coating deposited onto a substrate in  
such a way
that the coating is subjected to in-plane compressive residual  
stresses

after the deposition process. The coating has a cubic fcc crystal
structure before the deposition process, and also appears to be  
cubic fcc

with increased out-of-plane lattice parameter after the deposition. I
understand the increased out-of-plane lattice parameter because the
stresses are compressive in nature and the XRD experiment collects
information on the diffracting planes that are parallel to the sample
surface. However, I have the following question:

Since the residual stresses are compressive in nature, the fcc crystal
structure will become distorted after the deposition process, and  
strictly
will be no longer cubic. The change in the shape of the unit cell  
is most
likely a function of the orientation of the unit cell with respect  
to the

direction of the residual stresses. Thus, the cube can change to
tetrahedron, rhombohedral, etc. If the stresses are large enough in
magnitude (bout 1000 MPa), why the XRD pattern still shows a cubic  
crystal

structure (there are no additional peaks, peak splitting, etc).

Thanks in advance

Angel

Re: Level of Preferred Orientation

[Luca Lutterotti]

Dear Bhuv,
yes it is possible to evaluate it. Normally it should be sufficient to 
compute the F2 index from the spherical harmonic coefficient.
The problem may be is that TOPAS does not have such computation inside. 
So the other way is to export the coefficients, to hope they are some 
standard one and input them in a texture program that can compute F2 or 
texture strength index.

There could be some problems:
- if you have reduced the image to only one spectrum than using the 
harmonic apparatus what you get as F2 it could be it is not at all 
representative of the real texture strength as you are not fitting the 
real texture.
- as the texture coverage you have is for sure very small and 
insufficient, the harmonic coefficient will be strongly correlated with 
other errors and as the harmonic is not robust at all in such cases you 
are likely to get big errors in F2.

I would suggest one thing. If the Rwp decreases only 1%, why to use the 
harmonic texture correction at all?
A texture correction should be used (and especially the harmonic one) 
having a high level of confidence on the method, its effect and 
knowledge of the real texture of your sample and geometry/texture 
connections. Otherwise is just a black box that may lead to more errors 
than corrections.

Best regards,
Luca Lutterotti
On Apr 1, 2005, at 17:44, P. Bhuv wrote:
Hi,
I would like to discuss a couple of questions raised by a referee;-(
I am not sure if it is ethical or not - I thought it is better to ask
the way than .
1.
I have used very (very very)small amount of sample to collect a powder
pattern and I have corrected possible graininess with spherical
harmonics to account for small discrepancies in some of the peaks (to
give an idea - the Rwp decreased only 1% on correction - if the numbers
mean anything). Is it possible to estimate the level of preferred
orientation, if one uses a spherical harmonics correction? (I know
preferred orientation is not the right term to use here, in the first
place)
2.
The data I have collected is on a image plate (only one frame). Also, I
have used a z-matrix (rigid body) and allowing small meaningful changes
in bond lengths, angles, and torsions, i.e., z-matrix of the type (in
TOPAS):
A1
X2 A1 1.855 min 1.8 max 1.9
X3 X2 1.649 min 1.6 max 1.7  A1 114.987 min 113 max 116
X4 X3 1.649 min 1.6 max 1.7  X2  x4x3x2 122.80 min 122 max 123 A1
169.5 min 160 max 175




In such a case, is it possible to give (any meaningful) Standard
Uncertainties for the atom positions, (also) given the fact that the
atoms are not refined independently?
Thanks for any wise comments in advance,
Bhuv

N. Bhuvanesh
Texas AM Univ.
Coll. Stn., TX


__
Do you Yahoo!?
Make Yahoo! your home page
http://www.yahoo.com/r/hs

Re: Size Strain In GSAS

[Luca Lutterotti]

Dear Apu,
I know I will start up a good debate here, but size-strain analysis 
with GSAS is a non-sense. The program was not written with that purpose 
in mind and in fact it does not contains the instrumental aberration 
part of the broadening that is necessary for such computation.
Indeed it is possible to get at end some size-strain data, but quite 
hard as you have to do all correction later and out of the program. So 
it is like using GSAS for peak fitting, so better to use a peak fitting 
dedicated program.

Best wishes,
Luca Lutterotti
On Mar 25, 2005, at 7:15, [EMAIL PROTECTED] wrote:
Dear All,
I am trying to perform Rietveld refinement on a very simple system 
using GSAS. I have obtained a reasonable fit except the peak widths.

 I want to use the size and strain refinement option in GSAS to make 
the fit well.

Please tell me how to use the SIZE STRAIN refinement option in GSAS.
P.S. I am using the EXPGUI.
Thanks in advace.
Regards,
Apu
/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
 Apu Sarkar
Research Fellow
Variable Energy Cyclotron Centre
Kolkata 700 064
phone: 91-33-2337-1230 (extn. 3190)
Fax: 91-33-2334-6871
INDIA
/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/

Re: Size Strain In GSAS

[Luca Lutterotti]

Dear Apu,
difficult to say without seeing the pattern with your actual fitting. 
Broadening with small domain size is normally more easy to fit. It 
could be you didn't use the proper function or refines all necessary 
parameters, or there is an anisotropic broadening or faulting.
Every sample/analysis has his own story.
Try to put a picture of the fitting somewhere on the web and post here 
a link to the picture as attachments are not permitted in the list. 
This would be better as everyone can see it and give you some 
suggestions.

Luca
On Mar 25, 2005, at 12:00, [EMAIL PROTECTED] wrote:
Dear Prof. Lutterotti,
 I was also aware of the fact that GSAS is not made for Size Strain 
analysis. I got interested to use the Size strain refinement feature 
of GSAS only after going through the article :
Size-strain line broadening analysis of the ceria round-robin sample 
by Prof. D. Balzar et. al. Journal of Applied Crys. 37(2004)911-924.

In that round robin results they have reported the size strain 
obtained from GSAS.

I my case also when I am trying with GSAS, the diffraction pattern is 
fitting well except the peak braodening. I think this brodening is due 
to small domain size effect. I that case how will I obatin a good fit 
with GSAS.

Thanking you.
Best Regards,
Apu



/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
Apu Sarkar
Research Fellow
Variable Energy Cyclotron Centre
Kolkata 700 064
phone: 91-33-2337-1230 (extn. 3190)
Fax:   91-33-2334-6871
INDIA
/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
- Original Message -
From: Luca Lutterotti [EMAIL PROTECTED]
Date: Friday, March 25, 2005 3:31 pm
Dear Apu,
I know I will start up a good debate here, but size-strain
analysis
with GSAS is a non-sense. The program was not written with that
purpose
in mind and in fact it does not contains the instrumental
aberration
part of the broadening that is necessary for such computation.
Indeed it is possible to get at end some size-strain data, but
quite
hard as you have to do all correction later and out of the
program. So
it is like using GSAS for peak fitting, so better to use a peak
fitting
dedicated program.
Best wishes,
Luca Lutterotti
On Mar 25, 2005, at 7:15, [EMAIL PROTECTED] wrote:
Dear All,
I am trying to perform Rietveld refinement on a very simple
system
using GSAS. I have obtained a reasonable fit except the peak widths.
 I want to use the size and strain refinement option in GSAS to
make
the fit well.
Please tell me how to use the SIZE STRAIN refinement option in GSAS.
P.S. I am using the EXPGUI.
Thanks in advace.
Regards,
Apu
/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
 Apu Sarkar
Research Fellow
Variable Energy Cyclotron Centre
Kolkata 700 064
phone: 91-33-2337-1230 (extn. 3190)
Fax: 91-33-2334-6871
INDIA
/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/

Re: spherical hamonics

[Luca Lutterotti]

Even if the sample has a rolling (orthorhombic) sample symmetry, in a 
Bragg-Brentano pure experiment you see it as a cylindrical symmetry as 
you cannot distinguish between rotations around the normal to the 
sample. If you use a lower symmetry some of the spherical harmonic 
coefficients will not have a true effect on your spectrum and you 
cannot refine them.

Luca
On Feb 18, 2005, at 17:10, Yaroslav Mudryk wrote:
Hi everyone,
I tried to use spherical harmonics incorporated in EXPGUI/GSAS for 
modelling a preferential orientation in my sample. I used a 
cylindrical sample symmetry and it worked fine but I am confused about 
using such type of symmetry for a flat sample (Bragg-Brentano 
goniometer). The rolling (mmm) symmetry gave me a texture parameter 
about 400, which I can not accept. I would appreciate any comments 
related to this topic.

One more question: Does GSAS or any other software have any option for 
visualization of March-Dollase multi-axis preferential orientation?

sorry for using your time,
Yaroslav
Yaroslav Mudryk
252 Spedding Hall
Ames Laboratory
Ames, IA 50011, USA
Phone: 1-(515)-233-2041

Re: back loading / texture effects

[Luca Lutterotti]

Dear all,
with the occasion offered by this message I would like to spend few 
words about the spinning method to reduce texture effects.

In the Bragg-Brentano (or theta-2theta scanning case with sample 
surface normal to the scattering vector) spinning the sample around its 
normal does not reduce texture effects. This because the sample is in 
the center of an hypothetical pole figure and changing the so called 
phi or alpha angle does not change the texture. From a diffraction 
point of view the crystallographic planes diffracting are the ones 
parallel to the surface and turning them around their normal does not 
change nothing.
Actually due to the divergence of the beam there is a small effect, but 
it is very small, because it is like moving half a degree or maximum a 
couple of degrees from the center of the pole figure and unless you 
have an epitaxial thin film the change is unappreciable.
What in reality happens during spinning is that if the beam spot is not 
circular, but a line, you are sampling more volume in the sample (so it 
is equivalent to reducing grain size as Dipo Omotoso was pointing out) 
and this in some cases was erroneously attributed to decreasing texture 
effects.

So in the end when someone is selling you a spinning attachment for a 
Bragg-Brentano instrument because it help reducing texture effects, it 
is a lie (well, they may be don't know it is a lie).

Sorry, but it is a lot of time I desired to share this idea on the 
community and when I see still today these attachments sold around to 
reduce texture effects I cannot avoid to think about it (and laugh).

Luca Lutterotti
On Sep 9, 2004, at 16:30, Omotoso, Oladipo wrote:
Dear Andreas,
This may not be an option for your sample but grinding the sample to 
less
than 5 micron may help prevent fall out.  In this size region, you may 
not
need to spin the sample to reduce texture effects.

Dipo Omotoso

Re: SPAM on Rietveld list under my name

[Luca Lutterotti]

On Jul 21, 2004, at 2:02 PM, Alan Hewat wrote:
... Of course, this is just some-one impersonating me 
Armel, we know you are ;-))
Luca

Re: Quantitive analysis

[Luca Lutterotti]

Analysis without internal standard (for example for bulk materials) can 
be done with Maud for glasses of other common amorphous phases.
http://www.ing.unitn.it/~luttero/maud
there is one example, plus a publication on line.

Luca Lutterotti
On May 6, 2004, at 4:56 PM, Robert Mauricot wrote:
Dear all,
I have a powder diffraction of an amorphous multiphase material. I 
want to do a quantitative analysis of the amorphous phase.  Can anyone 
tell me what software does it.

Sincery
R.mauricot
Cemes-CNRS
Toulouse 31077 France
Laboratoire  NaNomat

Re: Natrite - Na2 CO3

[Luca Lutterotti]

On Sunday, November 12, 2000, at 06:36 PM, Armel Le Bail wrote:

And, yes, I have a legal leased copy of the ICDD PDF-2 CD-ROM, and I'm
not willing to violate copyright laws.

What copyright ? The atomic coordinates in ICSD, CSD and most (+50%) 
of the ICDD dcalc,dobs,Iobs,Icalc are taken by these companies in
papers published in  500 journals claiming also to possess the
copyright.

The question "who really possess the copyright" of such data

Also my 2 cents (it cost a little bit more in Italy),

just reading the copyright agreement the authors sign with the AIP (J. Appl. Phys., I 
have just a copy on my desk, I have to search for others) when submitting a paper:

".. 
The author(s) reserve the following rights:
..
(2) The right, after publication by AIP, to grant or refuse permission to third 
parties to republish all or part of the article or translations thereof. In the case 
of whole articles, such third parties must obtain AIP's written permission as well. 
However, such permission will not refused by AIP except at the direction of the 
author..."


I don't know for other journals but probably it is something similar. So base on the 
above my comment could be:
 I have only three entries in the ICSD but no one asked me for such permission. And 
given his comments also no one asked to Armel who has a lot more entries.

Now who is violating the copyright?

Also I want to see some comment on that


Best regards,
    Luca Lutterotti

Ps - Even if I am in Italy, I also have paid for the ICSD when it was selling much 
less copies but the cost is still the same now.


-------Luca Lutterotti
 Dipartimento di 
Ingegneria dei Materiali, Universita' di Trento,
 via Mesiano 77, 38050 Trento, Italy

 e-mail address : [EMAIL PROTECTED]
 Home page : 
http://www.ing.unitn.it/~luttero
 Mirror: 
http://www.ccp14.ac.uk/ccp/web-mirrors/lutterotti/~luttero/

 Phone number 
:+39-0461-88-2414
-Fax : +39-0461-88-1977-

Re: Peak Shape variation

[Luca Lutterotti]

So, thanks to the mail of Leonid Solovyov (referring to the GSAS manual for
the so call "subcell/supercell" broadening) I found out what I was not able
to understand from the Kirk and from the Bergmann mails (and searching on
my books, literature).
The subcell is only a way to simulate in part broadening due to faulting.
I wonder to know why people use criptic words for what was described 50
years ago in a clear way (for example by Warren). The result is that, when
I asked if the strange broadening is due to faulting or other things I got
a reply that it's subcell instead. Have people lost this way what is the
origin of these effects? Are we going to a future where we will not read
any more the old literature and renaming and rediscovering any sort of
physical phenomena?

Just to end, broadening due to faulting (unless is very poor) need not only
to model anisotropic peak width but also asymmetry, peak shift and
splitting. See Warren book for more. or try Maud.

Best regards,
    Luca Lutterotti


 
  Dear All,
 
  I am trying to carry out Rietveld refinement on a sample that has
  very obvious peak shape variation; probably due to subcell and
  supercell peaks. I believe there is a way to deal with this in GSAS,
  but I can't quite work out the best way.
 
  I'd be grateful for any tips
 
  Caroline
 
 
  Caroline Kirk
 
 
 This may not be helpful to your specified query but if you have a Bruker
 XRD with Topas Rietveld software - Topas has an option to apply spherical
 harmonics not only to Preferred orientation, but also anisotropic
 peak broadening, peak displacements (e.g., due to stress/strain) and
 some other parameters as well.
 
http://www.bruker-axs.com
 
 ...
 
 (I am not sure what other Rietveld programs allow this as well?)
 Lachlan M. D. Cranswick


 The program Maud (see my web pages) also models anisotropic peak broadening
 using the Popa (see on J. Appl. Cryst. of 1998, May-June?) model. It's an
 advanced harmonic expansion method were the Laue group of the phase imposes
 some obvious constraints on the harmonics to respect symmetries.

 There is another problem to know.  Is the observed strange peak shape
 simply anisotropy or there are other effects, like superstructure peak
 broadening, asymmetry and peak displacement by faulting etc.?
 In that case you need some special treatments (a.k.a Warren theories for
 twin, stacking faults and/or antiphase boundary). Maud can be used in this
 case but the actual general model only works for bcc, fcc, hcp structures.
 No general approach available up to now.

 Probably you may give some more information about the material and what
 kind of strange peak shape you are observing.

  Best regards,
  Luca Lutterotti

As Caroline has described, the peak shape is anisotropic due to
subcell/supercell behaviour. I will explain, how I have solved
this problem with BGMN:

PARAM=b1sub=0_0^0.1 PARAM=supfactor=1_0^1 b1sup=supfactor*b1sub //
B1=ifthenelse(mod(h+k+l,2),b1sub,b1sup)

This text is part of the structure description input file.
It is for the case of cubic bodycentered subcell/cubic primitive
supercell. Of course, BGMN may handle (positiv definite) broadenings
according to a Tensor of stage 4 (spheric harmonics of 4th order),
too. See ANISO4 at www.bgmn.de. Of course, each value may declared to be
ANISO4.

J"org Bergmann, Dresden
[EMAIL PROTECTED]



---Luca Lutterotti
 Dipartimento di Ingegneria dei Materiali, Universita' di Trento,
 via Mesiano 77, 38050 Trento, Italy

 e-mail address : [EMAIL PROTECTED]
 Home page : http://www.ing.unitn.it/~luttero
 Mirror: http://www.ccp14.ac.uk/ccp/web-mirrors/lutterotti/~luttero/

 Phone number :+39-0461-88-2414
-Fax : +39-0461-88-1977-

Re: Peak Shape variation

[Luca Lutterotti]

 Dear All,

 I am trying to carry out Rietveld refinement on a sample that has
 very obvious peak shape variation; probably due to subcell and
 supercell peaks. I believe there is a way to deal with this in GSAS,
 but I can't quite work out the best way.

 I'd be grateful for any tips

 Caroline


 Caroline Kirk


This may not be helpful to your specified query but if you have a Bruker
XRD with Topas Rietveld software - Topas has an option to apply spherical
harmonics not only to Preferred orientation, but also anisotropic
peak broadening, peak displacements (e.g., due to stress/strain) and
some other parameters as well.

   http://www.bruker-axs.com

...

(I am not sure what other Rietveld programs allow this as well?)
Lachlan M. D. Cranswick


The program Maud (see my web pages) also models anisotropic peak broadening
using the Popa (see on J. Appl. Cryst. of 1998, May-June?) model. It's an
advanced harmonic expansion method were the Laue group of the phase imposes
some obvious constraints on the harmonics to respect symmetries.

There is another problem to know.  Is the observed strange peak shape
simply anisotropy or there are other effects, like superstructure peak
broadening, asymmetry and peak displacement by faulting etc.?
In that case you need some special treatments (a.k.a Warren theories for
twin, stacking faults and/or antiphase boundary). Maud can be used in this
case but the actual general model only works for bcc, fcc, hcp structures.
No general approach available up to now.

Probably you may give some more information about the material and what
kind of strange peak shape you are observing.

Best regards,
Luca Lutterotti



---Luca Lutterotti
 Dipartimento di Ingegneria dei Materiali, Universita' di Trento,
 via Mesiano 77, 38050 Trento, Italy

 e-mail address : [EMAIL PROTECTED]
 Home page : http://www.ing.unitn.it/~luttero
 Mirror: http://www.ccp14.ac.uk/ccp/web-mirrors/lutterotti/~luttero/

 Phone number :+39-0461-88-2414
-Fax : +39-0461-88-1977-

Re: crystallite size determination

[Luca Lutterotti]

How does one handle the problem of bimodal particle size distributions by
diffraction techniques?  My previous experience at particle size measurements
using laser light scattering indicates non-monomodality is the norm rather
than the exception.  Can powder diffraction resolve this?

The more easy method is to use in the Rietveld two equal phases with
different crystallites and microstrains (or different line-broadening).
Obviously the two phases must have the same crystallographic parameters;
better to have a program allowing to keep the two phases in sync while
refining some parameters. Out of the Rietveld the Warren-Averbach method
(fourier extraction) should obtain the bimodal distribution and using
analytical shapes you can use the same trick of two peaks for any
reflection with the same angular position.

Another approach is the IT method of Guerin et al. (Acta Cryst. 88?). I
builded a program for using it (the IT) including the microstrains (not in
the original work). One advantage is that you are not limited by an
analytical peak function and the fit become perfect.
The results of that work and a testing on the accuracy of bi-modal
distribution analysis are in L. Lutterotti  P. Scardi, Adv. in X-ray Anal.
35, 577.

Best regards,
Luca Lutterotti




---Luca Lutterotti
 Dipartimento di Ingegneria dei Materiali, Universita' di Trento,
 via Mesiano 77, 38050 Trento, Italy

 e-mail address : [EMAIL PROTECTED]
 Home page : http://www.ing.unitn.it/~luttero
 Mirror: http://www.ccp14.ac.uk/ccp/web-mirrors/lutterotti/~luttero/

 Phone number :+39-0461-88-2414
-Fax : +39-0461-88-1977-

Re: Stress

[Luca Lutterotti]

Keller wrote,
You cannot measure stress from a diffraction experiment but (try to)
calculate it from the strain which you can measure.  Please specify:  is it
macro-st.rain (=residual strain -- line shift) on polycrystalline solids or

I start to be a little bit concerned about all those people claiming and
pointing out that diffraction don't measure a residual stress but a
residual strain.
Keeping this concept a step forward than we must say also that diffraction
don't measure a residual strain at all but a d-spacing change or even more
not a d-spacing but an angular position shift (if not a TOF etc) and so on.
And also, can you really be sure that the line shift you see is a strain?
(Just to go to the extreme).

Also, this reasoning will give the conclusion that no one technique is able
to measure a stress directly; most of them measure a displacement (and
convert the displacement to a stress or load using a know stiffness, like
diffraction), some measure other physical properties (light trasmission
etc.).

So, my own idea is that people who don't know how to transform strain in
stress will measure only strain and the other are measuring stresses.

Let me stress the audience about that; may be is that I am an engineer and
not a physicist or chemist.

best regards,
Luca Lutterotti




---Luca Lutterotti
 Dipartimento di Ingegneria dei Materiali, Universita' di Trento,
 via Mesiano 77, 38050 Trento, Italy

 e-mail address : [EMAIL PROTECTED]
 Home page : http://www.ing.unitn.it/~luttero
 Mirror: http://www.ccp14.ac.uk/ccp/web-mirrors/lutterotti/~luttero/

 Phone number :+39-0461-88-2414
-Fax : +39-0461-88-1977-

Re: Comments on Importance of matching software with hardware

[Luca Lutterotti]

On Thu, 25 Mar 1999, Brian H. Toby wrote:

 Plotting in Q sounds good to me.


Well, in my opinion anyone has some reasons to prefer uniformity of
plotting (only one standard some time is good) or optimizing views (custom
representation, d, Q or 2-theta...). May be, as pointed by Alan Hewat,
better to use a representation that can be understood by non-experts also
(if we want someone else would read our works).

Jon Wright wrote:
Horses for courses... shouldn't a fit show information which all has
approximately equal weighting in the minimisation algorithm? In the same
way that difference/esd is often more illuminating than just a
plain difference curve.

I would like to focus more attention on the lines by Jon.
I am actually plotting my data using Sqrt(Intensity) instead of Intensity.
You have several advantages from that:
- first the plot is at iso-error. In the residual you can easily
distinguish statistical errors from model errors.
- small peaks are more visibles. Try it on the quartz; you will not need
anymore to zoom the plot on the other peaks.

Just my 0.2 cents,

best regards,
Luca Lutterotti



---Luca Lutterotti
 Dipartimento di Ingegneria dei Materiali, Universita' di Trento,
 via Mesiano 77, 38050 Trento, Italy

 e-mail address : [EMAIL PROTECTED]
 Home page : http://www.ing.unitn.it/~luttero
 Mirror: http://www.ccp14.ac.uk/ccp/web-mirrors/lutterotti/~luttero/

 Phone number :+39-0461-88-2414
-Fax : +39-0461-88-1977-

Re: BaSiF6 or CaSiF6 structures, thanks

[Luca Lutterotti]

Thanks to all for sending me the informations and sorry; I should find
by myself the BaSiF6 structure in ICSD, but in reality I look in there for
the CaSiF6 or similar structure (ABX6 and tetragonal), so I miss the BaSiF6
and I found some references on it just on the web.

In any case thanks for the very fast help,

Luca Lutterotti



---Luca Lutterotti
 Dipartimento di Ingegneria dei Materiali, Universita' di Trento,
 via Mesiano 77, 38050 Trento, Italy

 e-mail address : [EMAIL PROTECTED]
 Home page : http://www.ing.unitn.it/~luttero
 Mirror: http://www.ccp14.ac.uk/ccp/web-mirrors/lutterotti/~luttero/

 Phone number :+39-0461-88-2414
-Fax : +39-0461-88-1977-

BaSiF6 or CaSiF6 structures

[Luca Lutterotti]

Did someone know the structure for one of these phases.
I didn't find them on the ICSD but I notice that at
http://fact.jst.go.jp/cr-vrml.html
there is the BaSiF6 included.
So it should be that someone has found the structure at least for this one.

Thanks in advance,

Luca Lutterotti



---Luca Lutterotti
 Dipartimento di Ingegneria dei Materiali, Universita' di Trento,
 via Mesiano 77, 38050 Trento, Italy

 e-mail address : [EMAIL PROTECTED]
 Home page : http://www.ing.unitn.it/~luttero
 Mirror: http://www.ccp14.ac.uk/ccp/web-mirrors/lutterotti/~luttero/

 Phone number :+39-0461-88-2414
-Fax : +39-0461-88-1977-