Thank you everybody, I definitely got some useful insights into my problem, which will help me see this analysis towards a successful end.
Many thanks, Alexandros > Hi Alex, > > I agree with everything Carlo and Matthew said. > > As you say, Li is very light and so the scattering should be weak compared > to Fe. It will also die out much more quickly with "k" than the Fe (or > Se) > scattering will. So, if you have enough k-range, simply starting your fit > at higher k than normal (perhaps 4 or 5 Ang^-1) or increasing the k-weight > used in the Fourier transform (perhaps to 3 or 4) would de-emphasize the > Se-Li scattering to a level that it was safe(r) to ignore. > > FWIW, I would imagine that trying to fit coordination number or sigma^2 > for > Se-Li at percent-level concentrations would not work very well. If you did > indeed get values that were clearly telling you that there was definitely > Se-Li scattering contributing, I would wonder if there was something else > going on (say, from another ligand, some multiple scattering, or some > other > phase). > > The formula for the Einstein temperature is a scale factor times > "coth(theta/(2t)) / (r_mass * theta)" where t is the temperature, theta > the Einstein temperature, and r_mass the reduced mass of the atoms in the > path. See > > https://github.com/xraypy/xraylarch/blob/726136d0184d9a006546002722b7573f6c675357/larch/xafs/sigma2_models.py#L19 > > for details. This will not include S0^2 -- they are conceptually totally > different. > > As Carlo said, the sigma^2 in the EXAFS equation does not distinguish > between static and thermal disorder. But if you have > temperature-dependent > data, modeling the sigma2 values as a static offset + a term that depended > on temperature with an Einstein model would be a fine way to go. > > Hope that helps! > > > On Thu, May 27, 2021 at 9:43 AM Alexandros Deltsidis < > adeltsi...@iesl.forth.gr> wrote: > >> Dear mailing list, >> >> I am currently analyzing some EXAFS data. I am studying a Lix(C5H5N)FeSe >> system in a temperature grid that extends from 20 K to 300 K and I have >> 4 >> such datasets which correspond to different amount of doping (x). Right >> now, im focusing on fitting the 1st coordination cell, in Artemis for >> the >> Se K-edge. My starting model is the simple P4/nmm FeSe. So, in my system >> the 1st coordination cell, in the Se K-edge, co _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit
