Hi Ryan, feff.inp doesn't have much more than a list of x,y,z coordinates for the atoms in the cluster, so if you have these you are most of the way there! What you really need is a set of coordinates: x,y,z,ipot where ipot is an index (0 through 7) that identifies a unique atomic Potential: you'll need a different one for each atomic species, and a special one (the one marked 0) to signify the absorbing atom. feff.inp also needs the list of atomic Potentials. I'd start with a feff.inp generated from Atoms (or Artemis) for a crystal and edit from there. You'd just need to alter the Potentials and Atoms sections. Note that the central atom is denoted by IPOT=0, not as the atom at x=y=z=0, though that is convenient. For simulated clusters, that means you might be able to make many feff.inp files simply by selecting different atoms to be the central atom. Is that enough of a start or do you need more hints? --Matt