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
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