[Ifeffit] Inequivalent atomic positions (V2O5 xerogel)

[Douglas Langie da Silva]

Dear all,

I am working with EXAFS data of V2O5 xerogel. In this form, the V2O5
present a monoclinic structure formed by bi-layers of VO5 pyramids
intercalated with water molecules. Fig 1 attached presents a view of the
V2O5 xerogel structure. There are two Vanadium atoms per unit cell, each
one surrounded by oxygen atoms at distinct distances, characterizing two
inequivalent sites.
My question is how to fit the data in dartemis considering the two
inequivalent positions?

My first approach was run Feff two times. Then I get two theoretical
models, one for V1 atoms and the other for the V2 atoms. Each of Feff runs
are present attached as model V1 and model V2. After that I transfer the
paths of the first shell of each model to dartesmis data windows (fig 2)
and proceed with the fit. We pay attention in the site fraction of each
vanadium atom in order to setup the S02 parameter for each model.  Without
attempting at this point with the numbers, the final results are present in
Fig. 3 e 4. Fig 4 presents the log file and the results for the each patch.

My question is: this procedure is valid?

Since now thak you.

-- 
Douglas Langie da Silva
Instituto de Física e Matemática
Departamento de Física
Universidade Federal de Pelotas
Campus Universiário s/n
CP 354
Pelotas/RS
CEP 96010-900
55 53 32757477
55 53 32757345

Douglas Langie da Silva
Physics Department
Federal University of Pelotas
POBox 354
Pelotas/RS
ZCode 96010-900
55 53 32757477
55 53 32757345
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