[Ifeffit] [howto] configurational average in EXAFS with FEFF

Mauro Rovezzi rovezzi at esrf.fr
Tue Mar 27 14:34:26 CDT 2007


I don't quote your answer because I would like to add some more elements
to specify what I'm searching for.

In my previous post I have used the term "cluster" in a wrong way, that
is I was thinking at the crystal-box (normally less than 216 atoms) used
in the ab-initio density functional theory calculations and "doped" with
few percent (< 10%) of an absorbing atoms. For example, if we put 5
absorbing atoms in a box of 64 (that represent the crystal host) we have
5 possible configurations for our FEFF calculation and is impossible in
an EXAFS fit to include all the important paths (too many!).

My idea to take into account the numerical simulation and combine it
with the experimental EXAFS data could be to use the pair radial
distribution function extracted from the simulation, average the
configurations, recalculate paths and proceed in the fit.

Well, I hope now is more clear... In any case, thank you for the useful


Frenkel, Anatoly wrote:
> Mauro, 
> If I do understand your question correctly, you may be asking how to handle a multiple of inequivalent sites in atomic clusters with N atoms, where each atom generates a unique sequence of single- and multiple-scattering paths. A possible solution is given in this article:
> D. Glasner and A. I. Frenkel 
> Geometrical characteristics of regular polyhedra: Application to EXAFS studies of nanoclusters 
> AIP Conf. Proc. 882 , 746-748 (2007). <https://exchange2000.bnl.gov/exchange/frenkel/Drafts/RE:%20%5BIfeffit%5D%20%5Bhowto%5D%20configurational%20average%20in%20EXAFS%20with%20FEFF.EML/XAFS13-Proc/clusters-geometry.pdf>  
> The PDF is here:
> http://pubweb.bnl.gov/users/frenkel/www/XAFS13-Proc/clusters-geometry.pdf
> It is the same type of averaging and radial distribution analysis approach that you are proposing unless I misunderstood your question.
> Anatoly

Mauro Rovezzi <rovezzi at esrf.fr>
PhD student - GILDA BM08 c/o ESRF (Grenoble, FR)

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