Theoretical study of local structures and EPR parameters for xV2O5-(100 − x)[0.8NaPO3-0.2ZnO]: V4 + glasses at different concentrations

Abstract

The electron paramagnetic resonance parameters and local structures for V4+ in xV2O5-(100−x)[0.8NaPO3-0.2ZnO] glasses are theoretically investigated by using the perturbation formulas for tetragonally compressed octahedral 3d1 clusters. Polynomial, custom and power law functions are applied to describe the concentration variations of covalency factor N, relatively tetragonal compression ratio ρ, core polarization constant κ and reduction factor H. The concentration dependences of the measured electron paramagnetic resonance parameters are suitably reproduced, and the PL functions are found to be the optimal with the lowest mean absolute percentage deviation from the experimental data. The [VO6]8− clusters exhibit moderately decreasing N, rapidly increasing ρ, slightly decreasing κ and moderately increasing H with x. The calculated decreasing local optical basicity Λloc also supports the declining trend of covalency factor. The theoretical study of the microscopic mechanisms for the concentration dependences of the relevant quantities are discussed in view of the impurity local behaviors with x due to mixed alkali effect.