module FMS: Full Multiple Scattering

This module carries out a full multiple scattering XANES calculation for a cluster centered on the absorbing atom. Thus all multiple-scattering paths within this cluster are summed to infinite order. This is useful for XANES calculations, but usually cannot be used for EXAFS analysis. FMS loses accuracy beyond $k =
(l_{\mathrm{max}}+1)/r_{\mathrm{mt}}$, which is typically about 4 Å$^{-1}$ since the muffin-tin radius $r_{\mathrm{mt}}$ is typically about 1 Å.