A model study on cluster size effects of resonant X-ray emission spectra

Cluster size dependence of X-ray absorption spectra (XAS), X-ray photoemission spectra (XPS), and resonant X-ray emission spectra (RXES) are theoretically studied with a one-dimensional d-p model, which describes qualitatively effects of translational symmetry for nominally d(0) (or f(0)) compounds such as TiO2 (CeO2). It is shown that RXES depends more sensitively on the cluster size than XAS and XPS, so that RXES is a useful probe in studying the duality between itinerant and localized characters of 3d or 4f electrons. From results calculated by changing the cluster size and parameter values such as p-d hybridization strength, d-d Coulomb interaction etc., it is explained why the experimental Ce 4f-3d RXES of CeO2 is well reproduced by calculations with a single-cation impurity Anderson model, but the Ti 3d-2p RXES of TiO2 is not well reproduced.