Theoretical Studies of the Local Structures and EPR Spectra for VO2+ in MB4O7 (M = Zn, Cd) Glasses.

Electron spin resonance spectral parameters (g factors g‖ g⊥ and hyperfine structure constants A‖, A⊥) of a tetragonal V4+ centers in MB4O7 (M = Zn, Cd) are theoretically investigated by using the perturbation formulae for a 3d1 ion in tetragonally compressed octahedra. In these formulae, the contributions to the g factors from the tetragonal distortion, characterized by the tetragonal field parameters Ds and Dt are taken into account by considering the local structures of the ligand octahedron around the V4+ due to the Jahn-Teller effect. Based on the calculations, the ligand octahedra around V4+ are suggested to suffer about 5.7% and 4.3% relative compression along C4 axis for MB4O7 glasses with M = Zn and Cd, respectively, and negative signs of the hyperfine structure constants Ag‖ and Ag⊥ for V4+ centers in MB4O7 glasses were suggested in the discussion. [ABSTRACT FROM AUTHOR]