We have performed the self-consistent full multiple-scattering analysis of the spin-dependent Mn Kedge XANES (x-ray-absorption near-edge structure) of MnO and MnF2. Our approach is based on successive self-consistent-field spin-polarized calculations of sma11 clusters and full multiple-scattering calculations of XANES within large size clusters. We have considered a cluster of nine shells of surrounding atoms for the MnO case and five shells for the MnF2 case. We have succeeded in calculating the spin-dependent XANES over a 40-eV energy range in the continuum above the absorption threshold in agreement with experimental data. The results show that both the spin-dependent transition matrix element and Mn p partial density of states contribute to the spin-dependent Mn K-edge XANES of MnO and MnF2.
The local and partial density of states of the conduction band of solid neon in a large energy interval has been extracted from the analysis of the K-edge x-ray-absorption near-edge structure (XANES) spectrum by using a full multiple-scattering method. The absorption cross section for one-electron transitions from the Ne 1s level to the conduction-band final states in the solid Ne is predicted by first principles. The absorption cross section is described as due to an atomic factor and to a structure factor determined by the local and partial density of states for a large cluster formed by about 80 atoms. The experimental spectrum is obtained by describing the final state in the fully relaxed potential in the presence of the core hole. The exciton peak at threshold is shown to be due to the lowest unoccupied valence state pushed down in the bound-state region by the core hole. In the 100-eV XANES energy range the single-scattering approximation fails to predict the XANES of solid Ne indicating that the full multiplescattering approach is required. The present analysis allows us to identify strong two-electron excitations Is 2s 2p~1 s'2s 2p'c;p in the energy range of 30 eV above the E edge, involving monopole 2p~cp transitions to the lowest valence states at energy c, . The intensity of the two-electron excitations is found to be so strong that it should be considered in standard extended x-ray-absorption finestructure -XANES data analysis for local structure investigation.
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