X-RAY-ABSORPTION STUDY OF RHENIUM L3 AND L1 EDGES IN REO3 - MULTIPLE-SCATTERING APPROACH

We present ab initio calculations of x-ray-absorption fine structure for the Re L3 and L1 edges in crystalline ReO3 based on an exact curved-wave multiple-scattering approach. Good agreement between theoretical and experimental data has been found for both edges. We show that (1) as expected, the contribution of multiple-scattering signals from linear chains, like Re-O-Re and O-Re-O, is very large both in the L3- and L1-edge spectra due to the strong focusing effect caused by the middle atom; (2) the additional difference between two edges, besides the one in central-atom phase shifts and the pi factor, originates from the geometrical dependence of multiple-scattering terms on the final l state, especially for paths forming a right angle at the absorbing atom; (3) the fine structure above the L1 edge is a superposition of two signals from L1 and L2 edges with a very significant contribution of the latter.