Theoretical studies on the electron paramagnetic resonance parameters for the tetragonal VO2+ center in CaO-Al2O3-SiO2 system

In this work, the high order perturbation formulae of the electron paramagnetic resonance (EPR) parameters, g & A for a VO2+ 3d(1) ion in tetragonal symmetry (compressed octahedron) are adopted to theoretically study these parameters of the tetragonal VO2+ center in CaO-Al2O3-SiO2 system. Because the spin-orbit (SO) coupling parameter zeta(p) (approximate to 151 cm(-1)) of ligand O2- is close to that (approximate to 248 cm(-1)) of the central V4+ ion in the cluster [VO6](8-) with strong covalence, the effect of the SO coupling parameter zeta(p) 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 VO2+ center in CaO-Al2O3-SiO2 system due to Jahn-Teller effect is obtained from the analysis of the EPR parameters. The results are discussed.