Evaluation of multiple-scattering contribution in extended x-ray absorption fine structure for mo₄and mc₆clusters

We present a theoretical ab initio evaluation of the multiple-scattering contribution in the extended X-ray absorption fine structure for MO₄and MC₆clusters with M = Mg, Ca, Mn, Zn, Se, Sr, Mo, Ag, Te, Ba, Nd, Tb, W, Au or Bi. The dependence of the multiple-scattering signal on the absorber type, the photoelectron angular momentum and the local distortion is discussed. It is shown that the multiple-scattering contribution is significant in the photoelectron wave-vector range up to 6-7 Å^-1and strongly depends on both the path geometry and the atomic species involved in the scattering process.