[Ifeffit] ATOMS: Partial occupancies -how to edit .cif File

Wei Li weili at udel.edu
Tue Apr 23 19:10:07 CDT 2013


Hi, Kai, one way to do it (without editing the *.cif file) is calculate the
feff input file first, and edit the feff input file by changing a few Ni
atom to Fe atom.

Wei


On Tue, Apr 23, 2013 at 7:41 PM, Sanwald, Kai <kai.sanwald at tum.de> wrote:

>  Hi,
>
> I would like to fit the NiFe2O4 spinel structure to EXAFS data of mixed
> Ni/Fe-(hydro)xide films.
> However, ATOMS cannot deal with structures exhibiting crystal sites with
> partial occupancies.
> I know that this problem has been adressed to some extent on the
> mailing-list already in May 2012
> (see
> http://millenia.cars.aps.anl.gov/pipermail/ifeffit/2012-May/010544.html)
> and Bruce Ravel shortly outlined how to edit the .cif file in order to run
> ATOMS and FEFF6.
> Attached you find the NiFe2O4.cif file that I like to employ. I tried the
> following:
>
> 1. changed occupancy from 0.5 to 1 in line
> Ni1 Ni2+ 16 d 0.625 0.625 0.625 . 0.5 0
>
> 2. subsequently deleted line
>
> Fe2 Fe3+ 16 d 0.625 0.625 0.625 . 0.5 0
>
>
>  I got rid of the ATOMS warning concerning the partial occupancy but
> FEFF6 crashes due to atoms being postioned too closely to each other. I am
> pretty sure that my editing resulted in a change of the structure.
>
> I would be very glad if someone could explain to me in some detail how I
> need to edit the .cif.
>
>
>  Thank you very much for your help.
>
>
>  Best,
>
> Kai
>
>
>
>
>
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>
>


-- 
Wei Li

Postdoc researcher
Environmental Soil Chemistry Group
Delaware Environmental Institute
University of Delaware, Newark,19713
Tel:631-949-0663
http://ag.udel.edu/soilchem/li.html <http://ag.udel.edu/soilchem/>
Researcher ID: http://www.researcherid.com/rid/D-6289-2011
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