Systematics in the electronic structure of 3d transition-metal compounds

We have studied a wide range of 3d transition-metal compounds by a cluster configuration-interaction analysis of the metal 2p core-level photoemission spectra. Deduced values for the charge-transfer energy Δ and the d-d Coulomb repulsion U, defined with respect to the multiplet-averaged energies, show a smooth variation as functions of cation atomic number, ligand and cation valence. Many physical properties, however, show apparently irregular variation, which we attribute to d-d exchange or multiplet effects, which also reflect upon Δ_eff and U_eff defined with respect to the lowest multiplet energies.