Theoretical studies on the electron paramagnetic resonance parameters for the tetragonal VO^(2+) center in CaO-Al_(2)O_(3)-SiO_(2) system

In this work, the high order perturbation formulae of the electron paramagnetic resonance (EPR) parameters, g & A for a VO^(2+) 3d^(1) ion in tetragonal symmetry (compressed octahedron) are adopted to theoretically study these parameters of the tetragonal VO^(2+) center in CaO-Al_(2)O_(3)-SiO_(2)system. Because the spin-orbit (SO) coupling parameter ζp (≈151 cm^(−1) ) of ligand O^(2−) is close to that (≈248 cm^(−1) ) of the central V^(4+) ion in the cluster [VO_(6)]^( 8)_(−) with strong covalence, the effect of the SO coupling parameter ζp on EPR parameters are considered on the basis of cluster approach. The obtained EPR parameters show good agreement with the experimental values and need fewer adjustable parameters than previous studies. And the local structure of the tetragonal VO^(2+) center in CaO-Al_(2)O_(3)-SiO_(2)system due to Jahn-Teller effect is obtained from the analysis of the EPR parameters. The results are discussed.