Samy Ould-Chikh | 24 Jul 09:55 2016
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Bug Report importing file.

Hello,

I have some issue to import a file in Athena: just a simple x-y column (.txt attached with this email).

Ti K-edge.
Data range in the file  : 4916.30 up to 5436.88 eV.
Issue: only data up to 5260 eV are imported (see screenshot: bug-importation).

Version: Demeter 0.9.24
System: Windows 7 Professional SP1

Well, I hope it's just not me not being able to find a proper way to import the file...

Best Regards,
Samy Ould-Chikh

KAUST Catalysis Center
Bldg.3,Level 4, #4231
4700 King Abdullah University of Science & Technology
Thuwal 23955-6900
Kingdom of Saudi Arabia

Tel: +966 12 8084486
E-mail: samy.ouldchikh@...
Website:  http://kcc.kaust.edu.sa/Pages/Home.aspx

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This message and its contents including attachments are intended solely for the original recipient. If
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(Continue reading)

Irina Pi | 22 Jul 17:05 2016
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Help with Athena

Dear all, 

I am just getting started with XAFS projects and I am using Athena software for processing and analysing the data. I am learning how to use it, and I have a little problem. The thing is that when I plot the XANES data, the automatic created plot is not labeled and plus it doesn't have the option of selecting a point of the spectrum. I mean, when I want to choose E0 for example, I need to do it changing the number in the Athena screen, and I don't know exactly what I am choosing because it doesn't appear anything in the graph. Was I clear? Do you know any way which I could solve it?

Thank you very much,

Regards, 
Irina Pi. 
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Fowler, Joseph W. (Assoc | 21 Jul 20:27 2016

demeter installation in OSX El Capitan

Dear Yuan,

Thanks for the log file, but I’m afraid I don’t know what your Mac Ports problem is. The log file indicates a failure to fetch the archive at all. After waiting a day, did the problem go away?

My workplace has lots of rules about how and when to upgrade to El Cap. As a result, I have not done it myself yet. Have you visited the Mac Ports team’s page on OS X 10.11? https://trac.macports.org/wiki/ElCapitanProblems  There are no specific problems mentioning libcxx, I notice. Did you remember to re-install Mac Ports itself? If not, then problems are inevitable. Also, are Xcode and its command-line tools both updated to match the OS?

If you’ve followed all the upgrade instructions and cannot install libcxx, then I think you have a Mac Ports problem and should look to that project’s issue tracker (possibly filing an issue yourself).

Best wishes,
Joe Fowler
NIST Boulder Labs

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Ping, Yuan | 21 Jul 07:37 2016

demeter installation in OSX El Capitan

Dear all,

I recently upgraded my mac to OSX El Capitan, and tried to install demeter following the steps at http://bruceravel.github.io/demeter/

XQuartz 2.7.9 (xorg-server 1.17.4), Xcode 7.3.1, command line tools, “sudo port -v self update”, “port upgrade outdated” were all OK. When I tried “sudo port install xorg-server demeter”, it showed:


--->  Computing dependencies for xorg-server

--->  Cleaning xorg-server

--->  Computing dependencies for demeter

--->  Dependencies to be installed: ifeffit libgcc cctools llvm-3.8 libcxx libffi llvm_select gmp isl ld64 ld64-latest libmpc mpfr pgplot gcc5 ... (a long list)


Then after many attempts to fetch libcxx-3.7.1_0.darwin_15.x86_64.tbz2 from various websites, it showed:


Error: org.macports.archivefetch for port libcxx returned: archivefetch failed for libcxx <at> 3.7.1_0

Error: Failed to install libcxx

Please see the log file for port libcxx for details:

   /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_lang_libcxx/libcxx/main.log


The log file is attached. What should I do to fix it? Any suggestion will be appreciated.

Thanks.
Yuan




Attachment (main.log): application/octet-stream, 6618 bytes
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Neil M Schweitzer | 21 Jul 00:59 2016

determining reasonable fitting parameters

Being somewhere between a novice and an advanced user of XAS, I have two “philosophical” questions about EXAFS fitting (I hope this is the correct forum to ask them!). I also have a bug to report. I have included a project file of a CeO2 powder for those interested.

 

1)      Generally, I have developed my own methodology for EXAFS fitting which I think generates ok fits, at least from the standpoint that the red line seems to follow the blue line pretty closely. My question relates to interpreting the statistics of the fit. Generally, I am studying catalyst (i.e. very small metal or oxide nanoclusters supported on a different oxide phase). Due to the size of the clusters of interest, I wouldn’t expect them to resemble a bulk crystal, and therefore it is difficult for me to reduce the number of independent variables using know crystal structures. For example in this reference material, I am giving every single scattering path its own delR and ss, and using a single delE and SO2 for all the paths since they come from the same feff calculation. Once I am through with my own methodology, I can usually get a close fit even while making every variable a guess (refer to fit 17 in the project file). Admittedly, the reduced chi is rather large (5262) and the error of each of the DWF’s is the same magnitude as the value itself, which is troubling. However, if I use the best fit values of fit 17 and set all of the values except for the 3 DWF’s and generate a new fit, all of the statistics significantly improve even though the values of the DWF’s did not change at all (Fit 19). That is, merely setting the other variables improved the fit (the reduced chi square is now 2951) and improved the error of the guess variables (the errors of the DWF’s are cut close to half). Why is the fit better since none of the values actually changed, and why do the errors improve? How should I be reporting the statistics (i.e. the errors) in a publication? Should I report the fit 17 errors or the fit 19 errors for the DWF’s?

2)      In terms of the DWF’s in general, what value is considered too high? I know the DWF’s have a component that relates to temperature induced disorder in the scattering shell and a component that relates to physical disorder in the scattering shell, but what value would be considered too big for a sample measured at room temperature. I have seen values as high as 0.03 and 0.04 in presentations (sorry, no references) but these seems too large to me. At some point, if the sample is disordered enough, it seems like EXAFS is no longer an appropriate characterization tool to use. What value of DWF would that represent (for a sample measured at room temperature)?

3)      I found a bug in the log files in the history window. I am running Demeter 0.9.21 on Windows 7. When I generate a new fit, if I change the k-range of the fit, the k-range of previous fits in the history window will also change to the current range (e.g. fit 19 was run from 2.1-9.3, as shown in the data window. Fits 14-16 were run in smaller ranges). What’s even stranger, is if I go to a very old fit (i.e. fit 1 or 2 in the project file) and then go back to the new fit, the log file will report the k-range from the earlier fit, not the current fit. Obviously, this is making it very difficult to keep track of fits generated with different k-ranges. I have not tested to see if the R-range behaves similarly.

 

Neil

Attachment (CeO2_MEE.fpj): application/octet-stream, 1499 KiB
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Matthew Marcus | 19 Jul 05:10 2016

fitting of S XANES with arctans and gaussians

I'm trying to fit 37 micro-XANES spectra taken at the S K-edge, using the method discussed in the paper by
Manceau and Nagy "Quantitative analysis of sulfur functional groups
in natural organic matter by XANES spectroscopy", Geochimica et Cosmochimica Acta 99 (2012) 206–223. 
In this paper, they fit spectra to two arctangents and 6 gaussians,
with widths of the arctans slaved together and widths of gaussians 1-3 and 4-6 slaved (or all 6 to one value). 
I'm looking for recommendations as to how to do the fit.
They give prescriptions for how to set the initial estimates to give robust values.  Manceau has told me that
'Athena works quite well', but I don't see any obvious way there
to do the parameter constraints called for, or to keep peak heights from going negative.  Athena also has a
habit of assuming you want it to do the normalization
for you; I've already done that and need no further 'help'.  Any ideas?

I've tried using Genplot, but that offers no way to restrain parametsrs to ranges to keep them from going nuts.

PCA seems to want 6-8 components, so it's not all that helpful.  These spectra were taken at various spots on a
biological structure (abalone radula) so there's
no sense of sequence which would enable the use of evolving factor analysis or something like that.  LCF
doesn't give satisfying fits with the references I have.

I've attached a couple of the files, truncated to the range Manceau&Nagy fit to.  The originas were taken
over the range 2460-2550eV.
	mam
2459.8733	0.016383041
2460.1233	0.016094189
2460.3735	0.022025956
2460.6238	0.016678091
2460.8738	0.016311111
2461.124	0.019483142
2461.3743	0.01770903
2461.6245	0.022848981
2461.8745	0.018562062
2462.1248	0.020740321
2462.3748	0.020652939
2462.625	0.017123673
2462.8752	0.025094582
2463.1252	0.019867383
2463.3755	0.022139577
2463.6257	0.023213524
2463.8757	0.020676881
2464.126	0.025052877
2464.3762	0.029113997
2464.6262	0.026324339
2464.8765	0.023671083
2465.1267	0.028306101
2465.3767	0.026002042
2465.627	0.030652333
2465.8772	0.028775895
2466.1272	0.032816786
2466.3774	0.033937715
2466.6277	0.032948535
2466.8777	0.034721162
2467.1279	0.035310403
2467.3782	0.044202648
2467.6282	0.038343795
2467.8784	0.044291645
2468.1287	0.045460965
2468.3787	0.051915355
2468.6289	0.064561076
2468.8789	0.064293481
2469.1292	0.06745372
2469.3794	0.076904655
2469.6294	0.078936517
2469.8794	0.083785988
2470.1292	0.09224768
2470.3789	0.10311307
2470.6287	0.12705681
2470.8784	0.15507881
2471.1279	0.19775756
2471.3777	0.24674262
2471.6274	0.38095856
2471.8772	0.61600226
2472.127	0.95312738
2472.3767	1.3190417
2472.6262	1.579319
2472.876	1.6359525
2473.1257	1.5544981
2473.3755	1.4989064
2473.6252	1.5021619
2473.875	1.5229028
2474.1245	1.4984316
2474.3743	1.3305453
2474.624	1.0569189
2474.8738	0.83871508
2475.1235	0.74043173
2475.3733	0.70619929
2475.6228	0.73935717
2475.8726	0.8194145
2476.1223	0.87513489
2476.3721	0.88144314
2476.6218	0.90261424
2476.8716	0.89132398
2477.1211	0.89018643
2477.3708	0.8967182
2477.6206	0.90281725
2477.8704	0.94701087
2478.1201	0.94702822
2478.3699	0.97867304
2478.6194	1.0008969
2478.8691	1.0092386
2479.1189	1.0287796
2479.3687	1.08442
2479.6184	1.1615053
2479.8679	1.3039225
2480.1179	1.5145243
2480.3674	1.797269
2480.6172	2.0798359
2480.8669	2.2775149
2481.1167	2.3608608
2481.3662	2.3488405
2481.616	2.2907579
2481.8657	2.2880797
2482.1155	2.3719938
2482.3652	2.5308979
2482.615	2.589304
2482.8645	2.5814075
2483.1143	2.3856504
2483.364	2.1799946
2483.6138	1.9504212
2483.8635	1.7527013
2484.1133	1.5563732
2484.3628	1.4446132
2484.6125	1.3397398
2484.8623	1.2488514
2485.1121	1.2062074
2485.3618	1.141425
2485.6116	1.1280848
2485.8611	1.0882412
2486.1108	1.0844127
2486.3606	1.0722013
2486.6104	1.0759245
2486.8601	1.050091
2487.1099	1.0626349
2487.3596	1.0662534
2487.6091	1.0521868
2487.8589	1.0660895
2459.8232	0.0086620357
2460.0735	0.0090417974
2460.3235	0.033545561
2460.5737	0.0085842237
2460.824	0.0051017846
2461.074	0.011186908
2461.3242	0.017373042
2461.5742	0.015282798
2461.8245	0.020608777
2462.0747	0.030159647
2462.3247	0.037008617
2462.575	0.019812036
2462.825	0.017694598
2463.0752	0.021219229
2463.3252	0.025639383
2463.5754	0.022631068
2463.8257	0.014809187
2464.0757	0.016797649
2464.3259	0.020190042
2464.5759	0.015993463
2464.8262	0.023149636
2465.0764	0.025470076
2465.3264	0.019795895
2465.5767	0.026845468
2465.8267	0.018706912
2466.0769	0.033239357
2466.3269	0.034196496
2466.5771	0.025028745
2466.8274	0.034550779
2467.0774	0.039939508
2467.3276	0.025766766
2467.5776	0.042343114
2467.8279	0.023223488
2468.0779	0.048359003
2468.3281	0.040589523
2468.5784	0.043160751
2468.8284	0.051982671
2469.0786	0.059320733
2469.3286	0.077092245
2469.5789	0.065575883
2469.8289	0.082144961
2470.0784	0.070433557
2470.3281	0.084788643
2470.5779	0.10309343
2470.8274	0.11019815
2471.0771	0.13859501
2471.3269	0.19976343
2471.5767	0.25412217
2471.8264	0.34704304
2472.0759	0.54530066
2472.3257	0.78615826
2472.5754	1.0521393
2472.8252	1.2056561
2473.0747	1.3237689
2473.3245	1.4084748
2473.5742	1.4852122
2473.824	1.5177881
2474.0735	1.4640881
2474.3232	1.3413973
2474.573	1.1608815
2474.8228	1.008761
2475.0725	0.8627153
2475.322	0.85124922
2475.5718	0.86840338
2475.8213	0.90438408
2476.071	0.96190357
2476.3208	0.98449355
2476.5706	0.95443678
2476.8203	0.94638139
2477.0698	0.89626169
2477.3196	0.85532951
2477.5693	0.8831256
2477.8191	0.88665426
2478.0686	0.90146577
2478.3184	0.92120427
2478.5681	0.90238905
2478.8179	0.94114095
2479.0674	1.0159788
2479.3171	1.0523196
2479.5669	1.1367817
2479.8167	1.2791884
2480.0664	1.501315
2480.3159	1.8128476
2480.5657	2.2177896
2480.8152	2.4746833
2481.0649	2.6505656
2481.3147	2.7177446
2481.5645	2.7476342
2481.8142	2.9169872
2482.0637	3.0258553
2482.3135	3.2625239
2482.5632	3.2067261
2482.813	3.0880082
2483.0625	2.8586359
2483.3123	2.5289466
2483.562	2.2037165
2483.8118	1.9437176
2484.0613	1.7121388
2484.311	1.5392073
2484.5608	1.4665928
2484.8105	1.365666
2485.0603	1.2651333
2485.3098	1.2447017
2485.5596	1.2118043
2485.8091	1.1773263
2486.0588	1.1215008
2486.3086	1.1032519
2486.5583	1.0873834
2486.8081	1.0994042
2487.0576	1.100813
2487.3074	1.0825663
2487.5571	1.0809017
2487.8069	1.0712752
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M.F.Bertuzzo | 18 Jul 18:59 2016
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Artemis - Atom/Feff issues

Dear all,


Having a spot of trouble with Feff calculations at the moment, any help would be much appreciated.


A little info before I describe the problem:


I have performed Crystal14 calculations on a system to optimise its geometry. After completing this, I opened the output file in J-Ice so that I could then save the file in .pdb format, so I could then open it inside of Mercury (v3.8) which would then allow me to save the file as a .CIF, to be used for Feff a calculation in Artemis. All okay so far.


But, when I open the CIF file inside of Artemis it thinks that some of the atoms sit only 0.02Angstroms apart from one another - obviously wrong. Yet when the file is viewed in Mercury (or whatever graphical interface you wish to use) it correctly displays the atoms, as opposed to Artemis which is somehow populating 500+ atoms within a small distance of just 5 Angstroms.

Is this something to do with the Cluster size? I have tried to arbitrarily increase it to a higher number to prevent it from finding atoms just 0.02Angstroms apart, but even then it locates atoms 0.14Angstroms apart which is still wrong. 


I have attached the structure (in .XYZ format) I am trying to work on so you can view it as well as its CIF format that I have been trying to open up inside of Artemis to run Feff.



Thanks for any assistance!


Marcus

Postgraduate Researcher in Chemistry
University of Kent



Attachment (model3_occ.cif): chemical/x-cif, 2335 bytes
Attachment (structure_xyzformat.xyz): application/octet-stream, 29 KiB
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M.F.Bertuzzo | 18 Jul 18:57 2016
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Artemis - Atoms/Feff issues

Dear all,


Having a spot of trouble with Feff calculations at the moment, any help would be much appreciated.


A little info before I describe the problem:


I have performed Crystal14 calculations on a system to optimise its geometry. After completing this, I opened the output file in J-Ice so that I could then save the file in .pdb format, so I could then open it inside of Mercury (v3.8) which would then allow me to save the file as a .CIF, to be used for Feff a calculation in Artemis. All okay so far.


But, when I open the CIF file inside of Artemis it thinks that some of the atoms sit only 0.02Angstroms apart from one another - obviously wrong. Yet when the file is viewed in Mercury (or whatever graphical interface you wish to use) it correctly displays the atoms, as opposed to Artemis which is somehow populating 500+ atoms within a small distance of just 5 Angstroms.

Is this something to do with the Cluster size? I have tried to arbitrarily increase it to a higher number to prevent it from finding atoms just 0.02Angstroms apart, but even then it locates atoms 0.14Angstroms apart which is still wrong. 


I have attached the structure (in .XYZ format) I am trying to work on so you can view it as well as its CIF format that I have been trying to open up inside of Artemis to run Feff.



Thanks for any assistance!


Marcus

Postgraduate Researcher in Chemistry
University of Kent




Attachment (structure_xyzformat.xyz): chemical/x-xyz, 29 KiB
Attachment (model3_occ.cif): chemical/x-cif, 2335 bytes
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#GUPTA DISHA# | 15 Jul 11:21 2016
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Artemis Antisite Simulation


Dear All


I am trying to simulate data for antisite disorder for LFP data. I import the CIF file and make sum of all the paths and save the file as an artemis file. I do this for different ratios of Li/Fe sites. However, I want to compare all these data in Origin. How do I open these artemis files in Origin to see how my data varies with different Li/Fe antisites?


Thank you and Kind Regards


Ms. Disha Gupta 

PhD Student  

School of Materials Science & Engineering (MSE) 

Nanyang Technological University

50 Nanyang Avenue, Singapore 639798

Tel: (65) 84087404 | Email: disha001 <at> e.ntu.edu.sg



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Today's Topics:

   1. Artemis (FEFF) question (Louis Forto)
   2. Re: Artemis (FEFF) question (Matt Newville)
   3. Re: Artemis (FEFF) question (Bruce Ravel)


----------------------------------------------------------------------

Message: 1
Date: Tue, 12 Jul 2016 10:13:17 +0100
From: Louis Forto <cforto10-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: ifeffit-yJARRRr6MatTopXEvdbuMochTzHAynqa8htcxDm17Xw@public.gmane.org
Subject: [Ifeffit] Artemis (FEFF) question
Message-ID:
        <CAOfHeiQnRSZX98TrKvDasc2t1WB1gq1xBmboA_T3k3RwkBNbhQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
Content-Type: text/plain; charset="utf-8"

Dear All,

I am trying to run a FEFF calculations on a quaternary glass , when I
import crystalline data obtained from ICSD website and try to run FEFF to
calculate the scattering paths of nearest neighbour atoms relative to
absorbing atom, I get an error message that says

" generate one or more common positions and their occupancies sum to more
than 1".

I don't know how to go about this, any help , I will appreciate.

Thanks.
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------------------------------

Message: 2
Date: Tue, 12 Jul 2016 07:43:56 -0500
From: Matt Newville <newville-Gn9iRbd85Kk2LMHL4Co/2odd74u8MsAO@public.gmane.org>
To: XAFS Analysis using Ifeffit <ifeffit-yJARRRr6MatTopXEvdbuMochTzHAynqa8htcxDm17Xw@public.gmane.org>
Subject: Re: [Ifeffit] Artemis (FEFF) question
Message-ID:
        <CA+7ESbrV9eiFEbXbwV94JFdkS1TopLEYXqB1VOk7QEGEEhXv9g-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
Content-Type: text/plain; charset="utf-8"

Louis,

On Tue, Jul 12, 2016 at 4:13 AM, Louis Forto <cforto10-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> Dear All,
>
> I am trying to run a FEFF calculations on a quaternary glass , when I
> import crystalline data obtained from ICSD website and try to run FEFF to
> calculate the scattering paths of nearest neighbour atoms relative to
> absorbing atom, I get an error message that says
>
> " generate one or more common positions and their occupancies sum to more
> than 1".
>
> I don't know how to go about this, any help , I will appreciate.
>
>
Please post what you have done, including the file with the
crystallographic data (CIFS file?) and the resulting feff.inp file.

Not to pick on you specifically, and really this is for everyone on the
list:  The first response to many questions is of the form "give us more
information" and/or "we cant help you unless we understand what you are
doing".   I see this in many forums and contexts, not just here.  In all
such contexts,  most of the people in the "likely to answer group" (often a
group of 1 to 3 volunteers) just view these initial, incomplete questions
as a waste of time.  It sometimes makes some of us noticeably grouchy, and
much less likely to want to help.  Please learn to ask better questions
that inspire the people likely to know the answers to *want* to help you.
It's not a mystery how to ask better questions, but it is some extra work.
Then again you're asking for free help with your science problem, so some
extra work to get a good response is probably worth that effort.

Here is a hint: It turns out that Athena and Artemis have project files
that contain the full information about the analysis session specifically
so that these sessions can be shared.

--Matt
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Message: 3
Date: Tue, 12 Jul 2016 08:52:55 -0400
From: Bruce Ravel <bravel-IGkKxAqZmp0@public.gmane.org>
To: XAFS Analysis using Ifeffit <ifeffit-yJARRRr6MatTopXEvdbuMochTzHAynqa8htcxDm17Xw@public.gmane.org>
Subject: Re: [Ifeffit] Artemis (FEFF) question
Message-ID: <5784E827.1070506-IGkKxAqZmp0@public.gmane.org>
Content-Type: text/plain; charset=windows-1252; format=flowed

On 07/12/2016 08:43 AM, Matt Newville wrote:
> Louis,
>
> On Tue, Jul 12, 2016 at 4:13 AM, Louis Forto <cforto10-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
> <mailto:cforto10-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>> wrote:
>
>     Dear All,
>
>     I am trying to run a FEFF calculations on a quaternary glass , when
>     I import crystalline data obtained from ICSD website and try to run
>     FEFF to calculate the scattering paths of nearest neighbour atoms
>     relative to absorbing atom, I get an error message that says
>
>     " generate one or more common positions and their occupancies sum to
>     more than 1".
>
>     I don't know how to go about this, any help , I will appreciate.
>
>
> Please post what you have done, including the file with the
> crystallographic data (CIFS file?) and the resulting feff.inp file.
>
> Not to pick on you specifically, and really this is for everyone on the
> list:  The first response to many questions is of the form "give us more
> information" and/or "we cant help you unless we understand what you are
> doing".   I see this in many forums and contexts, not just here.  In all
> such contexts,  most of the people in the "likely to answer group"
> (often a group of 1 to 3 volunteers) just view these initial, incomplete
> questions as a waste of time.  It sometimes makes some of us noticeably
> grouchy, and much less likely to want to help.  Please learn to ask
> better questions that inspire the people likely to know the answers to
> *want* to help you.   It's not a mystery how to ask better questions,
> but it is some extra work.  Then again you're asking for free help with
> your science problem, so some extra work to get a good response is
> probably worth that effort.
>
> Here is a hint: It turns out that Athena and Artemis have project files
> that contain the full information about the analysis session
> specifically so that these sessions can be shared.


Couldn't agree more.  And I have certainly been among the grouchier of late.


That said, it is likely that this is your "problem" is essential the
same as this:

http://bruceravel.github.io/demeter/documents/Artemis/extended/dopants.html#crystal-data-with-partial-occupancy

In fact, I suspect that entire page is relevant to what you are doing.


B

--
  Bruce Ravel  ------------------------------------ bravel-F56T3RlMPU4@public.gmane.orgv

  National Institute of Standards and Technology
  Synchrotron Science Group at NSLS-II
  Building 743, Room 114
  Upton NY, 11973

  Homepage:    http://bruceravel.github.io/home/
  Software:    https://github.com/bruceravel
  Demeter:     http://bruceravel.github.io/demeter/


------------------------------

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Neil M Schweitzer | 14 Jul 20:05 2016

No Reference Foil... Continued

Thanks for the responses. When I had originally tried fitting the CeO2 data, the fit was awful, but I think it was because the Eo was really far off. I set it close to where it should be and was able to find a common feature in Io to calibrate the rest of the samples to.

 

That being said, fitting CeO2 is still quite difficult. I found a reference online (EXAFS analysis of the L3 edge of Ce in CeO2: effects of multielectron

excitations and final-state mixed valence: J. Synchrotron Rad. (1999). 6, 34-42) that, from my understanding, essentially suggests duplicating all the paths and using a second delta_Eo value for the duplicated paths while also weighing the SO2 of each set of paths based on the degeneracy of the excitations. This does tend to make the fit better (as one would expect from doubling the number of paths!), but does anyone know if this is a generally accepted correction for fitting ceria materials? Does anyone have a different reference that might help me? Thanks for all the help!

 

Neil

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fred.mosselmans | 13 Jul 19:54 2016
Picon

No Reference Foil

Dear Neil,

Sorry this may be too exact an interpretation of your English, but if you are looking at the exafs  then
calibration is normally pretty irrelevant as long as it is not wildly out, as you refine E0 anyway in the fitting.
The bond distances will be very little altered by this.

If you are looking at XANES and it is 3/4  then CeL3  as I am sure you know has two "white lines" for four and one for
three and the ratio of the two peaks can be used to
Look at oxidation state mixtures, I think  you should be able to align the peaks and fit the area e.g. Burnham
AD, Berry AJ, 2014, The effect of oxygen fugacity, melt composition, temperature and pressure on the
oxidation state of cerium in silicate melts, Chemical Geology, Vol:366, ISSN:0009-2541, Pages:52-60

Best wishes
Fred

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