Covalent effects for rare earth ions with 6, 8 and 12 neighbors

We extend overlap considerations of rare earth ions to: Crystal field splittings when the rare earth ion is surrounded by 6, 8 and 12 neighbors in Oh symmetry, overlap with F1-, O2-, and Cl1- ligands. The results are compared with electrostatic lattice sum calculations as well as with several experimental results. © 1967.