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Re: [Ifeffit] Ifeffit Digest, Vol 104, Issue 4
by Soham Mukherjee 06 Oct '11

06 Oct '11

Dear Ifeffit Community, The attachment didn't open ?! I am resending the same. In any case, I will give all the details :- The sample is a thin layer, it's pretty homogeneous and had no pinholes during measurements. The fit details are :- k_min = 2, k_max = 14 R_min = 1, R_max = 3 The potential is self consistent in these calculations Fitting was performed in the R-space Best regards, Soham. On Thu, Oct 6, 2011 at 12:50 PM, <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: Energy shift (Dr. Dariusz A. Zaj?c) > 2. Zinc Sulfide fitting (Soham Mukherjee) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Thu, 06 Oct 2011 08:45:05 +0200 > From: "Dr. Dariusz A. Zaj?c" <kicaj(a)ifj.edu.pl> > To: XAFS Analysis using Ifeffit <ifeffit(a)millenia.cars.aps.anl.gov> > Subject: Re: [Ifeffit] Energy shift > Message-ID: <4E8D4E71.2000309(a)ifj.edu.pl> > Content-Type: text/plain; charset="utf-8"; Format="flowed" > > Your attachment do not help in this case... > Do you know something more about sample? I suppose it is a thin layer. > Have you checked if you have no defects, vacancies, etc? > I suppose that you can follow instructions given in this post > http://millenia.cars.aps.anl.gov/pipermail/ifeffit/2009-January/008522.html > but you can be also interested in this topic: > http://millenia.cars.aps.anl.gov/pipermail/ifeffit/2009-June/004293.html > and especially in last posts. > you can also try this suggestion > http://millenia.cars.aps.anl.gov/pipermail/ifeffit/2010-June/009471.html > > In general - could you precise, what is k_{min} for your fit, and did > you use self consistent potential in calculations? > > > > > > W dniu 11-10-06 02:28, JeongEunSuk pisze: > > Thank Dariuz and Bruce. > > TiO is deposited on Si substrate and PtO is fabricated on TiO2. > > I measered EXAFS with Pt L3 edge(11563eV) and The model is decided > > from FEFF8.0. > > PtO has only fist shell like attached files So I chose the simple > > model with octahedral structure (probe atom Pt, others O) > > When the EXAFS was fitted by feffit, the variables were three eo(Enot > > in Artemis, energy shift), do1(distance factor), sigo1(debye-waller > > factor). > > the results of fit is as following > > variable best fit value uncertainty initial guess > > eo = 19.283398 1.726426 0.000000 > > do1 = -0.023227 0.009557 0.096000 > > sigo1 = 0.003790 0.000583 0.003047 > > r-factor: 11 > > reduced-chi square: 95 > > > > Energy shift by fit shows an amount of difference from Pt L3 edge. It > > is my problem. > > To reduce the energy shift, I tried to remove background carefully > > again and to change distance Pt-O. > > However the result was failed. > > > > > > > > ------------------------------------------------------------------------ > > Date: Wed, 5 Oct 2011 08:24:16 +0200 > > From: kicaj(a)ifj.edu.pl > > To: ifeffit(a)millenia.cars.aps.anl.gov > > Subject: Re: [Ifeffit] Energy shift > > > > Hi, > > could say more precise what kind of energy shift you are talking > > about? the position of the white line or the Enot in Artemis. How big > > it is? Which version of Feff do you use? What do you mean writing > > "removing background carefully"? Background in the EXAFS fit? Any > > pictures to illustrate problem are welcome > > > > W dniu 11-10-05 03:25, JeongEunSuk pisze: > > > > Hell all > > I have the study for PtO nanoparticles with EXAFS. > > When I fitted the data to model, I had a problem for energy shift. > > I thought that the energy shift obtained from fitting must be > > below White line. However it was over white line. > > Although I removed background carefully and changed bond length in > > model, the energy shift was still big. > > I want to know other factors which affect energy shift. > > > > > > _______________________________________________ > > Ifeffit mailing list > > Ifeffit(a)millenia.cars.aps.anl.gov <mailto: > 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 > > > > > > _______________________________________________ > > Ifeffit mailing list > > Ifeffit(a)millenia.cars.aps.anl.gov > > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit >

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Zinc Sulfide fitting
by Soham Mukherjee 06 Oct '11

06 Oct '11

Zinc Sulfide exists largely in two phases, either the cubic zinc-blende (F-43m) phase, or the hexagonal wurtzite (P63cm) phase. The details of the NN distances are as follows :- 1. For cubic phase, the NN distances (Zinc to Sulfur bond lengths) are 2.3028 Angstroms each, 4 such bonds exist in a tetrahedral arrangement; 2. For hexagonal phase, there are 2 different NN distances (Zinc to Sulfur bond lengths) 3 bonds having the length 2.3421 Angstroms each, and 1 axially elongated bond of length 2.3465 Angstroms. So they differ only by 0.0044 Angstroms ! I am performing a first shell fit to Zinc Sulfide which exists in the wurtzite phase (hexagonal_P63cm). However, I could fit it quite well taking the cubic phase (Zinc blende_F-43m) as my starting model. The only thing is that since bond distances are higher in a hexagonal phase than the cubic phase, I end up with a considerable delr as I underestimated my starting bond length value. Taking a wurtzite model involves defining two different bond lengths (which differ only by 0.0044 Angstroms !), paths 1 and 2 in the FEFF, whose sigma^2 values are quite similar. This gives unusually large delr values and high sigma^2 for the longer axial bond, which looks suspicious ! Do I really need to define the two bond distances separately of so close values? Or taking a cubic phase will be sufficient? Please find the attached project file (artemis.apj) where I have tried out some simulations with both cubic and hexagonal models. With best regards, Soham.

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Energy shift
by JeongEunSuk 06 Oct '11

06 Oct '11

Hell all I have the study for PtO nanoparticles with EXAFS. When I fitted the data to model, I had a problem for energy shift. I thought that the energy shift obtained from fitting must be below White line. However it was over white line. Although I removed background carefully and changed bond length in model, the energy shift was still big. I want to know other factors which affect energy shift.

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Fit in TiO2
by Kleper Rocha 05 Oct '11

05 Oct '11

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Au-foil (fcc) splitted peak
by Kaiser, Julian 04 Oct '11

04 Oct '11

Dear Ifeffit Community, I'm trying to understand a basic question about an ordinary gold-foil in the fcc-crystal structure. If the spectra is plotted in the R-space, one will find two main-peaks at approx. 2.497 and 2.964 Angström that both should be attributed to the first shell. (see attached plot "Au_foil.pdf") Would this mean, one can find a peak-splitting in the 1st NN shell? And if yes, why? Maby I am compleately wrong and the second peak demonstrates already the second shell.(?) But I think the second shell should not start below 4.07825 Armströng. I think most of fcc metal crystals show this behavior. Of cause it also varys depending on the k-weight(kw=2 in the attachment). Thanks a lot in advanced, Julian ________________________________ Helmholtz-Zentrum Berlin für Materialien und Energie GmbH Mitglied der Hermann von Helmholtz-Gemeinschaft Deutscher Forschungszentren e.V. Aufsichtsrat: Vorsitzender Prof. Dr. Dr. h.c. mult. Joachim Treusch, stv. Vorsitzende Dr. Beatrix Vierkorn-Rudolph Geschäftsführer: Prof. Dr. Anke Rita Kaysser-Pyzalla, Dr. Ulrich Breuer Sitz Berlin, AG Charlottenburg, 89 HRB 5583 Postadresse: Hahn-Meitner-Platz 1 D-14109 Berlin http://www.helmholtz-berlin.de

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Absorption versus energy plot
by Francisco Garcia 04 Oct '11

04 Oct '11

Dear users, Can someone kindly explain how I can obtain the X-ray absorption versus energy plot (specifically which file contains the data) in FEFF9. I want to depict a single plot where I can clearly show the XANES and EXAFS regions. Thank you very much.

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Fit with Artemis in Demeter
by Kleper Rocha 30 Sep '11

30 Sep '11

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Preparation help with fly ash sample with diluted Tl
by Mengling Yi Stuckman 30 Sep '11

30 Sep '11

Dear Ifeffit Community, I am currently working on project "Evaluating Speciation of Thallium in Coal Fly Ash". The project was accepted by APS and we will conduct our measurement on beamline 5-BM-D. My fly ash sample has Tl concentration ranging from 0.5ppm to 13ppm. How can I know whether the sample can generate enough photon counts if using fluorescence mode? what would be the appropriate sample preparation procedure I should follow? Is there any interference I should pay attention to? I understand that I should use Hephaestus, but I don't know how to do that if my sample contains lots of different oxides. I attached the elemental composition in this email. Most metals should be in form of oxides, or sulfates. Any input would be highly appreciated, Mengling

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Re: [Ifeffit] Preparation help with fly ash sample with
by fred.mosselmans＠diamond.ac.uk 30 Sep '11

30 Sep '11

Dear Mengling, As Caroline Peacock from Leeds has successfully done Tl L3 microXAFS on some samples on I18 at diamond, I Have a little experience. She has a paper on the work currently in review. As Matt says if you have Pb in the sample your data is limited to just under 350 eV (10 k). Micro EXAFS past 10 k is quite hard but feasible and the big advantage is your localised concs. are possibly (probably?) a lot higher than for the bulk. If the Tl was equally distributed at 13 ppm max then micro Xanes might work, XAFS wont - but i think that's not likely. Thus with a local high concentration you might with time get 12 k XAFS from the Tl. As for using a total yield detector the big advantage is that they are count rate unlimited so you don't have to worry about count rate saturating your detector and can have it dead close to the sample to get the maximum Tl counts. Even with Al attenuation which will remove the Fe signal quicker than the Tl you are throwing away some Tl counts. Hence for XANES in particular it may be advantageous. Cheers Fred Prof. J F W Mosselmans Principal Beamline Scientist I18 Diamond Light Source Diamond House Harwell Campus Didcot Oxon OX11 ODE UK T 00 44 1235 778568 M 00 44 7785510211 E fred.mosselmans(a)diamond.ac.uk F 00 44 1235 778448 Never mind the W it's the tax that counts -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom

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Fly ash sample with diluted Tl
by Mengling Yi Stuckman 29 Sep '11

29 Sep '11

Dear Ifeffit Community, I am currently working on project "Evaluating Speciation of Thallium in Coal Fly Ash". The project was accepted by APS and we will conduct our measurement on beamline 5-BM-D. My fly ash sample has Tl concentration ranging from 0.5ppm to 13ppm. How can I know whether the sample can generate enough photon counts if using fluorescence mode? what would be the appropriate sample preparation procedure I should follow? Is there any interference I should pay attention to? I understand that I should use Hephaestus, but I don't know how to do that if my sample contains lots of different oxides. I attached the elemental composition in this email. Most metals should be in form of oxides, or sulfates. Any input would be highly appreciated, Mengling -- Mengling Yi Stuckman Graduate Research Assistant Civil and Environmental Engineering and Geodetic Science Ohio State University 2070 Neil Ave., Columbus, OH, 43210

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