[Ifeffit] ODP: XAFS fitting with multiple atomic sites of absorbing atom

[Zajac, Dariusz A.]

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 at 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
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