[Ifeffit] Re: XANES calculations

[John J. Rehr]

Dear Antonio,

  It appears that you've just experienced a common problem with hexagonal
space groups that one often needs a shift of the origin to get the "correct"
crystal structure. According to the atoms documentation (click on SHIFT in
Webatoms) there should be a note about this when you try to run, but
I didn't see it anywhere when I tried WEBATOMS today. Anyway the fix is to
introduce a MS shift vector of (0 0 .25), as in the atoms.inp file I sent
you. I think it might be useful if an appropriate shift were introduced by
default into the atoms database for very common lattice structures like
graphite, or otherwise to detail more precisely the coordinates of the shift
that one has to introduce by hand into atoms.inp (which is less desirable).
Maybe Bruce Ravel can consider these friendly suggestions in future releases
of atoms.

   I hope you don't mind,  but I've forwarded this msg to the ifeffit
list.

   Cheers,
   John


---------- Forwarded message ----------
Date: Mon, 16 Jan 2006 09:20:39 +0100
From: Antonio Politano <politano at fis.unical.it>
To: 'John J. Rehr' <jjr at leonardo.phys.washington.edu>
Subject: R: R: XANES calculations


Yes, I understand about stoichiometry. But I don't have understood why using
an atoms.inp file taken from the Atoms.inp archive I have six nearest
neighbours of the central assorber at 1,42 A. In your feff.inp file under
the ATOMS card there are only three nearest neighbours at 1,42 A (this is
correct!!!).

Thank you very much!!!

Antonio Politano