[Ifeffit] Inequivalent atomic positions (V2O5 xerogel)

Douglas Langie da Silva douglaslangie at gmail.com
Tue Mar 18 10:11:19 CDT 2014


Thanks Chris. Regards.


2014-03-18 11:54 GMT-03:00 Chris Patridge <patridge at buffalo.edu>:

> 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 <
> douglaslangie at gmail.com> 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
> > <Rav 1.jpg>
> > <Model v1.jpg>
> > <Model v2.jpg>
> > <Fig 3.jpg>
> > <Fig 4.jpg>
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-- 
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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