4fn-15d centroid shift in lanthanides and relation with anion polarizability, covalency, and cation electronegativity

摘要

Data collected on the centroid shift of the 5d-configuration of Ce3+ in oxide and fluoride compounds were recently analyzed with a model involving the correlated motion between 5d-electron and ligand electrons. The correlation effects are proportional to the polarizability of the anion ligands and it leads, like covalency, to lowering of the 5d-orbital energies. By means of ab initio Hartree-Fock-LCAO calculations including configuration interaction the contribution from covalency and correlated motion to the centroid shift are determined separately for Ce3+ in various compounds. It will be shown that in fluoride compounds, covalency provides an insignificant contribution. In oxides, polarizability appears to be of comparable importance as covalency. (C) 2003 Elsevier Science (USA). All rights reserved. [References: 17]