A COMBINATION OF QUASI-RELATIVISTIC PSEUDOPOTENTIAL AND LIGAND-FIELD CALCULATIONS FOR LANTHANOID COMPOUNDS

Improved energy-adjusted quasirelativistic pseudopotentials for lantha noid atoms with fixed valency are presented and tested in molecular ca lculations for CeO, CeF, EuO, GdO. YbO, and YbF. The pseudopotential c alculations treat the lanthanoid 4f shell as part of the core and yiel d accurate estimates for average bond lengths, vibrational frequencies and dissociation energies of all states belonging to a superconfigura tion. Information for each individual state of the considered supercon figuration may be obtained from subsequent ligand field model calculat ions. The results of this combined pseudopotential and ligand field ap proach (PPLFT) are compared to more accurate calculations with ab init io pseudopotentials that include the lanthanoid 4f orbitals explicitly in the valence shell and to available experimental data.