[Ifeffit] Hexagonal WO3 (Carlo Segre)

[Yordy Licea Fonseca]

Dear Carlo,

Thank you very much. The point is that we have obtained a Co Mo/W O4 solid
solution. It seems to me a very similar problem to that posted by Ying.

Good luck in yor work,

Yordy




2008/11/25 <ifeffit-request at millenia.cars.aps.anl.gov>

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>   1. Re: Hexagonal WO3 (Carlo Segre)
>      (Ying Zhou, Anorganisch-Chemisches Inst.)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 24 Nov 2008 19:47:48 +0100
> From: "Ying Zhou, Anorganisch-Chemisches Inst." <ying.zhou at aci.uzh.ch>
> Subject: Re: [Ifeffit] Hexagonal WO3 (Carlo Segre)
> To: segre at agni.phys.iit.edu, XAFS Analysis using Ifeffit
>        <ifeffit at millenia.cars.aps.anl.gov>
> Message-ID: <web-16396377 at idmailbe2b.unizh.ch>
> Content-Type: text/plain;charset=iso-8859-1;format="flowed"
>
> Dear Carlo
>
> Thanks very much for your nice suggestions. This is really what I want to
> know.
>
> Best wishes
> Ying
>
>
> On Mon, 24 Nov 2008 11:33:02 -0600 (CST)
>  Carlo Segre <segre at iit.edu> wrote:
> >
> > Hi Yordy:
> >
> > I have removed all the previous emails to keep the message short...
> >
> > On Sat, 22 Nov 2008, Yordy Licea Fonseca wrote:
> >
> >> Hi Carlo and Ying,
> >>
> >> Does it means that if the sample is a random solid solution at
> >>experimental
> >> temperature, in principle, you would be able to simulate the EXAFS
> spectra
> >> whichever be the Mo/W ratio in the second shell coordination in the
> >> Feff.inp, am I right?
> >>
> >
> > I am not quite sure what you are getting at but I think that the answer
> is
> > yes.  What you needto do is to have a single scattering path for each of
> > the two possibilities in the second shell (Mo or W) along with the first
> > shell path to O and then start fitting with minimal parameters.  For
> > example, if you know that the total number of atoms in the second shell
> is
> > 12 for this structure (and you are reasonably sure that this is the
> > correct structure), you can constrain the sum of the two occupation
> > factors to be equal to 12 provided that you have a reasonable
> > understanding of what the amplitude reduction factor might be.  You can
> > also start by constraining the delta R and sigma-squareds for the two
> > paths until you are sure that the fit makes sense and is stable.
> >
> > If you have data from both W and Mo edges, you have more leeway in your
> > fitting and you can begin to make a model which tries to figure out if
> > there is clustering of one kind of atom in the structure.  There are a
> > number of papers in the literature that do this (off the top of my head I
> > can think of one in particular by Shibata and Bunker for Au/Ag
> > nanoparticles but there are surely many more).  Ultimately you can
> develop
> > a nice model but the one thing that you can't really do too much is
> > include multiple scattering paths which include the atoms which are
> > substituted for one another.
> >
> > Hope this answers your question,
> >
> > Carlo
> >
> > --
> > Carlo U. Segre -- Professor of Physics
> > Associate Dean for Special Projects, Graduate College
> > Illinois Institute of Technology
> > Voice: 312.567.3498            Fax: 312.567.3494
> > segre at iit.edu   http://www.iit.edu/~segre   segre at debian.org
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> End of Ifeffit Digest, Vol 69, Issue 17
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-- 
Yordy E. Licea Fonseca
Departamento de Físico-Química
Instituto de Química-IQ/UFRJ
Laboratório de Catálise Heterogênea
Rio de Janeiro, RJ, CEP 21.949-909
Brasil
Email: yliceafonseca at gmail.com
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