Local structural parameters for the tetragonal Cr3+-VM and VM-Cr3+-VM centers in Cr3+-doped crystals were estimated by calculating their electron paramagnetic resonance zero-field splitting and g-factors using 2 theoretical models. One was the 2 spin–orbit parameter model in which the contribution due to the spin–orbit coupling of central d3 ion, and that due to the ligands, were included. The other was the conventional 1-spin–orbit parameter model in which only the contribution due to spin–orbit coupling of the central d3 ion was considered. The estimated tetragonal distortion, based upon the 2-spin–orbit parameter model was about 2.2 times that based upon the 1-spin–orbit parameter model, for both centers. It appeared that, for dn clusters with ligands having a large spin–orbit coupling coefficient, the contribution of the spin–orbit coupling of ligands to the electron paramagnetic resonance parameters could not be neglected. Therefore, the 2-spin–orbit parameter model was better for explaining the electron paramagnetic resonance parameters or for studying the local structures of clusters on the basis of electron paramagnetic resonance data.

Studies of the Local Structures for the Two Tetragonal Centers in AgCl:Cr3+ Crystals from EPR Parameters. W.C.Zheng, S.Y.Wu: Physica B, 1998, 252[3], 173-7