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The oxygen, sulfur, and 3d transition metal, Ti and Fe, K-edge XANES/ELNES spectra, with particular references to TiO 2 (rutile), TiS 2 , and α-Fe 2 O 3 , have been calculated by using full multiple-scattering (MS) theory and different size clusters. The comparison to experimental data has demonstrated that one would need so take account of higher coordination neighbors, i.e. so called long-range effects, in constructing molecular orbitals. The cluster size should be at least two times the cation-anion bond length in the case of anion taken as central atom, and cation-cation plus cation-anion bond lengths when cation is taken as center of cluster. Based on this general rule, we are able to reproduce we pre-edge peaks (including the crystal-field splitting) and obtain excellent agreements with experimental data. The detailed quantitative interpretation of the pre-edge structures of these three compounds is presented.
Wu et al. (Tue,) studied this question.