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

[Sanwald, Kai]

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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