High-order perturbation formulae of zero-field splittings D and E and g-factors for 3d3 ions in rhombic symmetry were established by using a 2-spin-orbit coupling parameter model in which not only the contribution due to the spin-orbit coupling of the central 3d3 ion but also that of the ligands was included. Based upon these formulae, all 5 electron paramagnetic resonance parameters for the Cl3+ ion at a rhombic defect site in the cubic crystal were explained by considering a suitable defect-induced lattice distortion. The relative importance of the various contributions to the electron paramagnetic resonance parameters arising from the spin-orbit couplings of the central 3d3 ion, the ligand ions and the mixed ones was considered. It could be seen that, for the 3d3 ions in crystals with ligands having a large spin-orbit coupling parameter, the contribution due to the spin-orbit coupling of ligands could not be neglected and that the 2-spin-orbit parameter model should be used in studies of electron paramagnetic resonance parameters.

Theoretical Investigations of the Zero-Field Splittings and g Factors for the Cr3+ Ion at the Rhombic Defect Site in the AgCl Crystal. S.Y.Wu, W.C.Zheng: Journal of Physics - Condensed Matter, 1998, 10[34], 7545-51