[Ifeffit] [ATOMS] supercell input file

Bruce Ravel bravel at bnl.gov
Fri Sep 19 10:11:06 CDT 2008


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.


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
 Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2
 Building 535A
 Upton NY, 11973

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