Dear Rana, could you specify how many independent data points and variables you have and you use for fitting? thnx darek -----Wiadomość oryginalna----- Od: ifeffit-bounces@millenia.cars.aps.anl.gov w imieniu Jatinkumar Rana Wysłano: Pn 2010-06-14 12:00 Do: Ifeffit users Temat: [Ifeffit] XAFS fitting with multiple atomic sites of absorbing atom Dear users, I have measured XAFS spectra on Mn and Fe edge on my material. The material contains 3 different atomic positions for Mn and 4 different atomic positions for Fe. Initially, I tried fitting Fe-edge/Mn-edge spectra using indiviual Fe/Mn atomic position one-by-one (i.e. first take one Fe/Mn position, calculate Feff paths, consider certain paths to fit specific R-range, then take another Fe/Mn position and do the same) but the fit was not good visually and in terms of goodness of fit parameters. Then, i tried fitting Fe-edge/Mn-edge spectra, taking into account all Fe/Mn atomic position together i.e. I separately calulated Feff paths for each Fe/Mn atomic position and summed up related paths from each Feff calculation for fitting a specific R-range. (The assumption being, the experimental Fe-edge/Mn-edge XAFS spectra has varying contribution from all Fe/Mn atomic position in crystal structure). Anybody in the group could comment about my approach to fit such problem ? Is there any specific strategy to fit such problem ? I would be thankful if you could suggest some literature available on such problems. Thanks in advance. Best regards, Rana _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit