[Ifeffit] atoms input file

[Matt Newville]

Hi Mohamed,

I'm not certain I understand what you're trying to do, but to add a
"dopant" or partial occupancy of an atom at a particular lattice site,
run atoms on the "pure" structure (UO2) and then replace some of the
"solvant" (U) with the "solute" (Ce) in the feff.inp.  See

  http://cars9.uchicago.edu/ifeffit/Doped

for more details.  If that's not what you're asking, let us know,

--Matt