[Ifeffit] The possibility of the defect concentration estimation by feff

[Iraida N. Demchenko]

Dear All, 

Do I understand correctly that using feff calculations it is impossible
to calculate the concentration of defects in a sample? I'll try to
explain my question with an example. Let us assume that we have a
(Ga,Mn)As sample, where Mn is a dopant. Comparing the experimental curve
(Mn K edge) with the theoretical spectrum, we see that the experimental
one is well described by a linear combination of two theoretical ones,
namely, substitutional manganese in the position of gallium (Mn_Ga) and
interstitial manganese (Mn_i) in proportions of 65 and 35%,
respectively.  

Is it possible to recalculate these phases weights (I mean Mn_Ga and
Mn_i) to the real concentration of the mentioned above defects in the
sample? For example, for the Mn_Ga model, ONE manganese atom was
considered per cluster of 900 atoms (FMS 7A). Does it make sense to
recalculate the stoichiometry (using cluster size) and, subsequently,
the weights of this model when compared to the experimental curve, which
will eventually give the selected defect concentration at the low level
(like ~0.2%). Do I understand it correctly? 

I will be very grateful for your help in understanding. 

Best, 

Iraida.
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