[Ifeffit] Trouble with Artemis
Hello; Trying to plot a fit in Artemis. My .dat files appear flat on y= zero in the plot window. they open fine in Athena. Any help would be appreciated. regards ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
Re: [Ifeffit] Trouble with Artemis
plots parameters, options are the same for Artemis and Athena? regards W dniu 11-08-03 08:23, Morgan Scott pisze: Hello; Trying to plot a fit in Artemis. My .dat files appear flat on y= zero in the plot window. they open fine in Athena. Any help would be appreciated. regards ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
[Ifeffit] Invitation to connect on LinkedIn
LinkedIn ifeffit, I'd like to add you to my professional network on LinkedIn. - Somaditya Somaditya Sen Research Associate at Physics Dept., UWM Greater Milwaukee Area Confirm that you know Somaditya Sen https://www.linkedin.com/e/o6ijfu-gqwaay89-k/isd/3744123338/3Yn0HeKq/ -- (c) 2011, LinkedIn Corporation___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
[Ifeffit] Athena: problems with LCF
Dear All, I acquired Cd L3-edge spectra of some binary and ternary mixtures in varying proportions and for the individual components. Then, I tried to fit the reference spectra to the spectra of the mixtures using linear combination fitting of Athena to get their abundance. However, results were disappointing despite all spectra were carefully energy calibrated and normalized, so I decided to create simple mathematical ternary mixtures by summing up the spectra of the individual reference spectra (edge step normalized) and tried the fitting again to exclude mixing-failures and check sensitivity of LCF with the idealized spectra. Unfortunately, LCF was also not able to reliable deconvolute these spectra into the individual reference spectra. Does anybody have an explanation for that? It would be nice if somebody could give me information about the mathematical fitting algorithm implemented in Athena. Thanks a lot! Wishes, Nina ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
Re: [Ifeffit] Fe K-edge second shell problems
Paul, have you considered explicitly multiple scattering from within the tetrahedron? The short distance you describe for the second shell might be consistent with that. Its pretty easy to write an expression in the fit routine that makes the MS path distances explicitly dependent on the SS paths (no new variables in the fit)--the number of MS paths is constrained by the geometry (tetrahedral). The order of scattering is probably just 3- and 4- legged MS paths, no higher (would give longer distances) I study arsenic, and so I've seen this approach described in the following paper on As: Voegelin et al (2007) Geochimica et Cosmochimica Acta v. 71, pp. 5804-5820. Look in the section 2.6 for the details. sorry if someone already answered this, ~~ Andrea L. Foster, Ph.D. U.S.G.S. WMESC 345 Middlfield Rd., MS 901 Menlo Park, CA 94025 T: 650-329-5437 F: 650-329-5491 ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
Re: [Ifeffit] Fe K-edge second shell problems
Hi Paul, Looking at your data, I agree that there does seem to be second-shell scattering present in the signal. Unfortunately, that most likely means that your material is not close to one of the obvious model compounds. One possibility to keep in mind is that you may have some kind of overlapping paths in that second shell--for example, partially Fe-Na and partially Fe-Ca, or an assortment of Fe-Na's at different distances. A clue can perhaps be obtained by noting the relative height of the peak near 2.3 angstroms compared with the large peak you've fit. As k- weight is raised from 0 to 1 to 2 to 3, the peak at 2.3 angstroms does not grow relative to the first peak. That suggests the scattering may be from another low-Z element like oxygen. So I'd tentatively try an Fe-O path around 2.7 angstroms with its own delR, ss, and N guessed. (Meanwhile, set N_1 to 4 to reduce correlations--you've said you expect the first shell to be tetrahedral.) Good luck--sounds like a stubborn one! --Scott Calvin Sarah Lawrence College On Aug 3, 2011, at 9:49 AM, Paul A Bingham wrote: Dear Ifeffit users, I have been struggling with this problem on and off for many months and I cannot resolve it - hopefully someone out there can help I have collected fluorescence Fe K-edge EXAFS of oxide glasses doped with low levels (0.2%) of Fe. The glasses are typified by their major components SiO2, Na2O, CaO and also low levels of Fe2O3 and CeO2 dopants. I'm currently trying to fit the Fe EXAFS. The first shell is relatively easy to fit and I'm reasonably happy with the fit I obtained using a tetrahedral Fe3+ standard, in this case FePO4. The fits are consistent, as I expected to find, with Fe3+ tetrahedrally-coordinated with four oxygens. The problem comes - and here's where I could really use some suggestions - when I try to fit second Fe-x distance. It seems clear to me that a second Fe-x distance (and possibly a third) are present in the data. However, despite expending a great deal of time I am unable to get a fit that appears anywhere near sensible and robust and for which the output parameters are sensible. I suspect the second Fe-x distance (I reckon about 2.8 Angstroms) to be Fe-Na but Fe-Ca, Fe-Si or Fe-O may also be possible. It's also possible that it is Fe-Fe or Fe-Ce. I have tried all of the obvious Fe model compounds (aegirine, clinopyroxine, etc) and also many others and I simply cannot get anything approaching a decent fit. The vast majority of distances in model compounds are Fe-O distances around 1.9-2.1A, then there is usually a gap until about 3.1A. I have checked my background subtraction and tried out many different options, changes and tweaks that I know or can find suggested but I cannot obtain a fit that is any good. And so I ask my colleagues out there who are more experienced than I with EXAFS - can anyone help with this conundrum? I have attached the Artemis file with the data and simple one-shell fit using FePO4 cif file; and the Athena file FYI. Thanks in advance for your time and I look forward very much to reading any suggestions you may have. Warm Regards Paul Bingham -- Dr. Paul A. Bingham Immobilisation Science Laboratory Dept. of Engineering Materials University of Sheffield Mappin Street Sheffield S1 3JD UK Email: p.a.bing...@sheffield.ac.uk Direct Line: (0114) 2225473 Bingham_Fe_EXAFS_Glass_Ifeffit_Artemis Bingham_Fe_EXAFS_Glass_Ifeffit_Athena.prjATT1..txt ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
[Ifeffit] Postdoctoral position at Yeshiva University
Dear IFEFFIT subscribers: Please find here the info about the job opening: Postdoctoral position at Yeshiva University Physics Department of Yeshiva University in New York City has immediate opening for a postdoctoral research associate position. The postdoc will investigate thermal, structural and electronic properties of nanocatalysts and contribute to the ongoing research in heterogeneous catalysis. He or she will be stationed at Brookhaven National Laboratory (BNL) and work closely with BNL departments (NSLS, Chemistry, Physics/Materials Science and the CFN) as well as the outside collaborators. Required qualifications: expert knowledge of XAFS and x-ray diffraction and experience with nanomaterials characterization. Hands on experience with vibrational spectroscopies (Raman, IR) and electron microscopy is a plus. The research will be performed under the direction of Prof. Anatoly Frenkel primarily at the Synchrotron Catalysis Consortium (http://www.yu.edu/scc https://webmail.bnl.gov/exchange/frenkel/Drafts/RE:%20[Ifeffit]%20Fe%20K-edge%20second%20shell%20problems.EML/redir.aspx?C=44fc2d9c1c7d43be96daee679b109becURL=http%3a%2f%2fwww.yu.edu%2fscc ) at the National Synchrotron Light Source. Applicants should forward cover letter and CV, and arrange for three letters of recommendation to be sent to Prof. Frenkel at anatoly.fren...@yu.edu. Yeshiva University is an Equal Opportunity Employer. Anatoly Frenkel, Ph.D., Professor Department of Physics, Yeshiva University 245 Lexington Avenue, New York, NY 10016 http://www.yu.edu/faculty/afrenkel https://webmail.bnl.gov/exchange/frenkel/Drafts/RE:%20[Ifeffit]%20Fe%20K-edge%20second%20shell%20problems.EML/redir.aspx?C=44fc2d9c1c7d43be96daee679b109becURL=http%3a%2f%2fwww.yu.edu%2ffaculty%2fafrenkel Spokesperson, Synchrotron Catalysis Consortium http://www.yu.edu/scc https://webmail.bnl.gov/exchange/frenkel/Drafts/RE:%20[Ifeffit]%20Fe%20K-edge%20second%20shell%20problems.EML/redir.aspx?C=44fc2d9c1c7d43be96daee679b109becURL=http%3a%2f%2fwww.yu.edu%2fscc Office: (212) 340-7827, Lab: (631) 344-3013, Email: anatoly.fren...@yu.edu winmail.dat___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
