Wu Xiao-Xuan

EPR parameters and defect structure of the tetrahedral Ti3+ defect center in beryl crystal

The EPR parameters (g factors g i and hyperfine structure constants A i , where i=x, y, z) of Ti3+ ion at the tetrahedral Si4+ site of beryl crystals are calculated within the rhombic symmetry approximation from the high-order perturbation formulas based on the two-spin-orbit (SO)-parameter model. In these formulas both the contribution due to the SO coupling parameter of the central 3d1 ion and that of ligand ions are considered. From the calculations, the defect structure of the Ti3+ defect center in beryl crystal is estimated and the EPR parameters g x , g y , g z and A y are reasonably explained. The values of the parameters A x and A z (which were not reported) are suggested and remain to be checked by the further experimental studies.

Theoretical studies of electron paramagnetic resonance parameters for Cr4+ ions in Ca2GeO4 crystals

The electron paramagnetic resonance (EPR) parameters (zero-field splitting D and g factors g(parallel to), g(perpendicular to)) of Cr4+ ions in Ca-2 GeO4 crystals have been calculated from the complete high-order perturbation formulas of EPR parameters for a 3d(2) ion in trigonal MX4 clusters. In these formulas, in addition to the contributions to EPR parameters from the widely used crystal-field (CF) mechanism, the contributions from the charge-transfer (CT) mechanism (which are often neglected) are included. From the calculations, it is found that for the high valence state 3d(n) ions in crystals, the reasonable explanation of EPR parameters (in particular, the g factors) should take both the CF and CT mechanisms into account.