Wouldn't you just put the atoms at the vertices of an icosahedron? That is, how would you know what was beyond the first shell? The feff.inp file below might be a good start. --Matt TITLE Fe at center of an icosahedron HOLE 1 1.0 Fe K edge CONTROL 1 1 1 1 PRINT 1 0 0 3 * set value to change near neighbor distance * from 1.902 (=sqrt(1 + phi^2)) to 2.500 RMULTIPLIER 1.31435 RMAX 3.0 POTENTIALS * ipot z label 0 26 Fe 1 26 Fe ATOMS 0.000000 0.000000 0.000000 0 0.000000 1.000000 1.618034 1 0.000000 -1.000000 1.618034 1 0.000000 1.000000 -1.618034 1 0.000000 -1.000000 -1.618034 1 1.000000 1.618034 0.000000 1 -1.000000 1.618034 0.000000 1 1.000000 -1.618034 0.000000 1 -1.000000 -1.618034 0.000000 1 1.618034 1.000000 0.000000 1 1.618034 -1.000000 0.000000 1 -1.618034 1.000000 0.000000 1 -1.618034 -1.000000 0.000000 1