Ab initio multiple-scattering calculations of the rhenium L₃ and L₁ edges XAFS in ReO₃

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. We show that (1) the contribution of multiple-scattering signals from linear chains, like Re O₃ Re and O — Re — O, is very large both in the L₃ and L₁-edge spectra due to the strong focussing effect caused by the middle atom; (2) the geometrical dependence of multiple-scattering terms on the final l state leads to the additional difference between signals from L₃ and L₁ edges, especially for paths forming a right angle at the absorbing atom; (3) the fine structure above L₁-edge is a superposition of two signals from L₁ and L₂ edges with a very significant contribution of this latter.