Carlos,

A Feff.inp file has exactly 1 absorbing element.  From this absorber, scattering paths to its neighboring atoms are found and the XAFS contribution calculated for each of these paths.

So you need to make 24 (or more?) separate Feff.inp files.  The list of atomic coordinates can be the same, but you can change which Ti atom is the absorber.  Be aware that each Feff calculation really needs to take place in its own directory (as Feff will overwrite output files), so you really want approximately 24 different directories, each with its own Feff.inp file.

Then you can add up all the contributions from all of the resulting feffNNNN.dat files.

We know this is slightly painful and that it really should be easier.  Bruce and I have started working on modifications to the Feff input / output mechanism that should eventually make this sort of thing easier.
We need help doing this!


--Matt

 

On Mon, Sep 29, 2014 at 10:44 AM, Carlos Triana Estupinan <ctrianae@unal.edu.co> wrote:
Dear
Feff group

I am Carlos Triana, and I want ask you the following.
I am trying to calculate the feff.inp file for a theoretical amorphous structure composed by a supercell with 24 Ti atoms surrounding by 48 oxygen atoms with different coordination. In amorphous materials or materials with distortions from regular crystals, the absorbing atoms may have different surroundings.
My question is how can I build the feff.inp file in this case, shall I define the 24 Ti atoms like absorbing atoms, because in this case the feff does not works. 
What can I do in this case, how can I build the feff.inp file with different environments

I will be very grateful for your help

--

Carlos Augusto Triana Estupiñan (C.A. Triana-E)
Physicist
M.Sc. In Physical Sciences-Research
PhD Student-Research
Ångströmlaboratoriet, Lägerhyddsv. 1
Solid State physics
Uppsala University, Box 534
751 21 Uppsala, Sweden
Tel: +46 018 471 3144
e-mail:carlos.triana@angstrom.uu.se
web:http://www.uu.se/


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--
--Matt Newville <newville at cars.uchicago.edu> 630-252-0431