Re: [Ifeffit] Inequivalent atomic positions (V2O5 xerogel)

Hello, I think it is valid. The model for v2o5 is tough to fit well at low R because the apical oxygen bond is so short that there is some significant overlap between the background and signal near 1 angstrom. Chris ******************************************** Dr. Christopher Patridge Assistant Professor of Chemistry Math and Natural Science Dept BFAC 009 D'Youville College 320 Porter Ave., Buffalo, NY 14150 716-829-8096 Sent from my iPhone

On Mar 18, 2014, at 10:31 AM, Douglas Langie da Silva wrote:

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 <Model v1.jpg> <Model v2.jpg> _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit