[Ifeffit] [ATOMS] supercell input file

[Bruce Ravel]

Mauro,

Your problem is a genuine bug.  When I go through the contents of the
cell to determine how many ipots to assign, the Fe atom gets noticed
and added to the list of species in the cell.  I should exclude the
absorber from consideration at that step.  

I don't see immediately how to fix that problem, but I'll try to come
up with a solution and check it into svn soon.

I can suggest a work-around.  It still requires editing the feff.inp
file generated, but it is a much less onerous editing chore:

  * In the atoms.inp file, change the iron atom to Ga and give it a
    tag -- something like this:
      Ga 0.444444444444444 0.555555555555555 0.3455528537 Abs

  * Change the value of the "core" keyword to the tag:
      core =	Abs

  * Run feff, and edit the first element of the potentials list.

That is still annoying, but much less so than the feff.inp file you
attached to your email.

B


On Friday 19 September 2008 10:40:04 Mauro Rovezzi wrote:
> Dear all,
>
> I would like to submit to your attention a problem with Atoms that I
> still do not understand. What I would like to do is to generate a FEFF
> input file starting from a supercell, that is repeating the unit cell
> NXxNYxNZ times and create the crystal with the resulting box.
>
> An example is given in the attached _test-atoms.inp_ created following
> this procedure: from wurtzite GaN (a,c cell parameters) that we describe
> with 2 atoms I reduce the symmetry and I use 4 atoms, then I create a 72
> atoms supercell - 4*(3x3x2) - that has 3ax3ax2c dimensions and finally I
> tell atoms to use "P1" space group in order to replicate the supercell
> in x,y,z space and shift at the center the absorbing atom.
>
> Here the *problem*: the resulting _test-feff8.inp_ present good values
> of distances but strangely it has generated an additional Fe potential
> (there is just 1 Fe absorbing atom in the box/list). This is annoying
> because I have to remove manually the wrong "ipot" to run FEFF.
>
> Is it a stupid mistake generating the Atoms input file or is it an odd
> behaviour?
>
> Cheers,
> Mauro
>
> PS: Atoms 3.0.1 (linux) 05/08/15
> PPS: Do not pay attention to coordinates and distances, these are just
> test-files!



-- 
 Bruce Ravel  ------------------------------------ bravel at bnl.gov

 National Institute of Standards and Technology
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