AB-INITIO CALCULATION ON CRYSTAL FIELDS OF SM2+ IN SOLIDS WITH CL ANDF LIGANDS

The linear combination of atomic orbitals (-molecular orbitals) crysta l-field theory in the context of the superposition model was used to c alculate the intrinsic crystal-field parameters for Sm2+ ions in solid s with Cl and F ligands at different interionic distances. The five ma in contributions: point charge, charge penetration, exchange, overlap, and covalency considered in the present work can reasonably describe the experimental results. A direct comparison between divalent and tri valent lanthanide ions leads to the conclusion that the. initial intri nsic crystal-field parameters and the power-law exponents correspondin g to the distance dependence for divalent lanthanide ions are larger t han those for trivalent lanthanide ions.