- Ifeffit - millenia.cars.aps.anl.gov

Question: About using polarization and ellipticity cards in FEFF
by xu dongbin 13 May '12

13 May '12

Hi, I would like to ask a question which has confused me for a few days. In my current case, I'm dealing with samples with c texture in the film normal. The sample was measured with linear polarized x-ray in both directions with the surface of sample parallel/perpendicular to the electrical field of x-ray. During measurement, the sample was always rotated around the film normal. Therefore, I think the parallel direction data can be treated with random orientated grains in the film plane. In order to describe this, I need use POLARIZATION and ELLIPTICITY cards in FEFF calculation. However, I'm not sure which case below is the correct one I should include in FEFF calculation for my case: a. POLARIZATION 1 1 0 ELLIPTICITY 1 0 0 1 b. ELLIPTICITY 1 0 0 1 I think these two cases should give the same calculation results, however, when I sum the paths in these two cases respectively using the same parameters(S02, E0, delR, sigma^2). The results give substantial difference. Can anyone help me to figure out this? Thanks&Regards!

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Debye function model, Math expression
by NIRAWAT THAMMAJAK 11 May '12

11 May '12

Hello, May I add more questions to this. I do a research on magnetic materials. Bond lenghts and geometries are really important to understand the magnetic interactions and I think EXAFS is the promising tool for this. I have measured the EXAFS spectra for quite a complex material system. There are 3 sites of absorbing atom (Fe) in the crystal structure, therefore I created 3 FEFF models to fit the data with different amplitudes. Closest neighbours are oxygen atoms, and then Li. The strongest scatterers are La atoms sitting ~4.26 angtrom away from the absorbing atom, which contribute a significant 3rd shell. Yes, there are many paths to include. Math expressions together with bulk structure details obtained from neutron diffraction help to minimise the parameters somewhat. However, there are thermal factorss, very small but too many of them. I measured my sample at 1.5 K, then sigma^2 are quite small. Could you please suggest any papers, models, or math expressions constraining these factors at low temperature. Would it be sensible to constrain them as 0, or a range of small numbers obtained from the significant shells? Thank you very much, Nirawat. On 24 August 2010 18:25, Frenkel, Anatoly <frenkel(a)bnl.gov> wrote: > Just to add: > These procedures, described in that article, can be easily implemented in > Mathematica. > Anatoly > > > ------------------------------ > *From:* ifeffit-bounces(a)millenia.cars.aps.anl.gov on behalf of Ravel, > Bruce > *Sent:* Tue 8/24/2010 1:23 PM > *To:* XAFS Analysis using Ifeffit > *Subject:* Re: [Ifeffit] debye function > > On Tuesday 24 August 2010 12:23:18 pm Kleber Daum Machado wrote: > > Hi, > > > > I'd like to know the explicit mathematical expressions that are > > represented by the functions debye(temp,thetad) and eins(temp,thetae). > > Are they given in some documentation file or article? > > See > > "Extended x-ray absorption fine structure Debye-Waller > factors. I. Monatomic crystals" > E. Sevillano, H. Meuth, J. J. Rehr > Phys. Rev. B 20, 4908–4911 (1979) > http://link.aps.org/doi/10.1103/PhysRevB.20.4908 > > B > > > -- > > Bruce Ravel ------------------------------------ bravel(a)bnl.gov > > National Institute of Standards and Technology > Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 > Building 535A > Upton NY, 11973 > > My homepage: http://xafs.org/BruceRavel > EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/ > _______________________________________________ > Ifeffit mailing list > Ifeffit(a)millenia.cars.aps.anl.gov > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > > _______________________________________________ > Ifeffit mailing list > Ifeffit(a)millenia.cars.aps.anl.gov > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > >

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Problem with Ifeffit 1.2.11 on Windows XP
by 최선희(Sun Hee Choi) 08 May '12

08 May '12

Dear XAFS colleagues, I use Ifeffit 1.2.11 on Windows 7 machine with no difficulty, but that version bothers me when applied to Windows XP. One of useful tips is to select a value from the plot, that is the use of Pluck Button. When I try to select a value with pluck button, a wrong value is grabbed. Hardly a right value is grabbed! This problem also occurs in point finder. And, ‘Indicator’ does not work at all…I cannot see vertical lines…. Please help me to resolve the problem. Sunny ------------------------------------------------------------ Pohang Accelerator Laboratory (PAL) / POSTECH San 31, Hyojadong, Namgu, Pohang 790-784 Republic of Korea -------------------------------------------------------------

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Re: [Ifeffit] Ifeffit Digest, Vol 111, Issue 5
by Christopher Thomas Chantler 07 May '12

07 May '12

Hi All There has been much discussion of this at the recent Q2XAFS meeting. Proceedings are I believe being reviewed at the moment. >From I think some consensus of those attending, the most critical and most portable data was [mu/rho] versus E, with uncertainties; or mu versus E. Secondary data such as k^2chi vs k or chi vs r etc remains valuable of courseŠ I hope this helps. With luck there will be much discussion of this in Beijing [if we can all get visas!] Chris ------------------------------------------------------------ Christopher Chantler, Professor, FAIP Editor-in-Chief, Radiation Physics and Chemistry Secretary, Steering Committee, International IUCr Commission on XAFS Vice-President (Australasia) International Radiation Physics Society School of Physics, University of Melbourne Parkville Victoria 3010 Australia +61-3-83445437 FAX +61-3-93474783 chantler(a)unimelb.edu.au chantler(a)me.com http://optics.ph.unimelb.edu.au/~chantler/xrayopt/xrayopt.html http://optics.ph.unimelb.edu.au/~chantler/home.html On 8/05/12 3:00 AM, "ifeffit-request(a)millenia.cars.aps.anl.gov" <ifeffit-request(a)millenia.cars.aps.anl.gov> wrote: >Send Ifeffit mailing list submissions to > ifeffit(a)millenia.cars.aps.anl.gov > >To subscribe or unsubscribe via the World Wide Web, visit > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit >or, via email, send a message with subject or body 'help' to > ifeffit-request(a)millenia.cars.aps.anl.gov > >You can reach the person managing the list at > ifeffit-owner(a)millenia.cars.aps.anl.gov > >When replying, please edit your Subject line so it is more specific >than "Re: Contents of Ifeffit digest..." > > >Today's Topics: > > 1. Re: Writing a paper (Bruce Ravel) > > >---------------------------------------------------------------------- > >Message: 1 >Date: Mon, 07 May 2012 12:32:16 -0400 >From: Bruce Ravel <bravel(a)bnl.gov> >To: XAFS Analysis using Ifeffit <ifeffit(a)millenia.cars.aps.anl.gov> >Subject: Re: [Ifeffit] Writing a paper >Message-ID: <3694643.vNiDHMscfl@lachesis> >Content-Type: text/plain; charset="us-ascii" > >On Monday, May 07, 2012 04:10:35 PM mattie.peck(a)huskers.unl.edu wrote: >> Hello Everyone, >> >> I am in the process of fitting XAFS data for a paper and I was wondering >> what type of information should should be included. I remember coming >> across a website that had this information on it awhile ago but I can't >> seem to find my way back. We would like to publish a qualitative XANES >> paper and an EXAFS paper. Any suggestions on the type of information >> (plots, tables, R-factor, etc.) that should be included in each paper >> separately would be appreciated. > >Was this the page you were looking for? > > http://xafs.org/Reporting_EXAFS_Analysis > >Incomplete, but useful. > >B > > >-- > > Bruce Ravel ------------------------------------ bravel(a)bnl.gov > > National Institute of Standards and Technology > Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 > Building 535A > Upton NY, 11973 > > Homepage: http://xafs.org/BruceRavel > Software: https://github.com/bruceravel > > >------------------------------ > >_______________________________________________ >Ifeffit mailing list >Ifeffit(a)millenia.cars.aps.anl.gov >http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > > >End of Ifeffit Digest, Vol 111, Issue 5 >*************************************** >

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Peak fitting in Excel
by Luanga Nchari 07 May '12

07 May '12

Hi folks, Does anybody know how to plot data for Gaussian and arctangent step peaks (from Athena) in Excel. I can't find the data after peak fitting. I've also searched in the Ifeffit mailing list archive. Cheers, Luanga

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Writing a paper
by mattie.peck＠huskers.unl.edu 07 May '12

07 May '12

Hello Everyone, I am in the process of fitting XAFS data for a paper and I was wondering what type of information should should be included. I remember coming across a website that had this information on it awhile ago but I can't seem to find my way back. We would like to publish a qualitative XANES paper and an EXAFS paper. Any suggestions on the type of information (plots, tables, R-factor, etc.) that should be included in each paper separately would be appreciated. Thanks, Matthea Peck

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third cumulant
by JeongEunSuk 07 May '12

07 May '12

Hello I measured temperature-dependent EXAFS at Pt L3 edge with Pt nanoparticles in room and high temperature(400 C). I have some questions about thermal vibration in EXAFS fit. I read that third and fourth culmulants related with phase and amplitude in anharmonic term, respectively. especially, I concerned third culmulant to relate with phase. As you know, the phase also relates with bonding length. So that, the bonding length between Pt-Pt pair considerably correlated with third culmulant. So I can't decide exact bonding length and third culmulant because their correlation. I think that the relation of both bonding length and third culmulant is similar to that of number and debye-waller factor. Is it right to find bonding length and third culmulant like finding number and debye-waller factor using k-weight?

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Re: [Ifeffit] (no subject)
by Anatoly I Frenkel 07 May '12

07 May '12

It sounds like a good idea but you will still need to know whether the best fit results for the bond length and third cumulant are correct. Since they are expected to vary widely for different cluster sizes and different substrates and different atmospheres, you should first try to see if your method will work for a more simple system where you know what the bond length and third cumulant should be, i.e. bulk Pt. Besides, you may find something similar to what you are proposing in Bus and v.Bokhoven's article. Anatoly Sent from my mobile phone, please forgive typos -----Original message----- From: JeongEunSuk <eunsuk1986(a)hotmail.com> To: ifeffit <ifeffit(a)millenia.cars.aps.anl.gov> Sent: Mon, May 7, 2012 04:02:06 GMT+00:00 Subject: [Ifeffit] (no subject) Hello I measured temperature-dependent EXAFS at Pt L3 edge with Pt nanoparticles in room and high temperature(400 C). I have some questions about thermal vibration in EXAFS fit. I read that third and fourth culmulants related with phase and amplitude in anharmonic term, respectively. especially, I concerned third culmulant to relate with phase. As you know, the phase also relates with bonding length. So that, the bonding length between Pt-Pt pair considerably correlated with third culmulant. So I can't decide exact bonding length and third culmulant because their correlation. I think that the relation of both bonding length and third culmulant is similar to that of number and debye-waller factor. Is it right to find bonding length and third culmulant like finding number and debye-waller factor using k-weight?

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(no subject)
by JeongEunSuk 06 May '12

06 May '12

Hello I measured temperature-dependent EXAFS at Pt L3 edge with Pt nanoparticles in room and high temperature(400 C). I have some questions about thermal vibration in EXAFS fit. I read that third and fourth culmulants related with phase and amplitude in anharmonic term, respectively. especially, I concerned third culmulant to relate with phase. As you know, the phase also relates with bonding length. So that, the bonding length between Pt-Pt pair considerably correlated with third culmulant. So I can't decide exact bonding length and third culmulant because their correlation. I think that the relation of both bonding length and third culmulant is similar to that of number and debye-waller factor. Is it right to find bonding length and third culmulant like finding number and debye-waller factor using k-weight?

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How to use ATOM on this file?
by Wei Li 06 May '12

06 May '12

Hello, Bruce, I have a *.cif, in which structure contains Zn and Al in the same site but diferent ratio. I cannot use ATOM to build a cluster for Feff. I am wonder if you could figure this out. Thanks in advance! best wishes yours Wei Li -- Wei Li Postdoc researcher Environmental Soil Chemistry Group Delaware Environmental Institute University of Delaware, Newark,19713 Tel:631-949-0663 http://ag.udel.edu/soilchem/li.html <http://ag.udel.edu/soilchem/>

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