Theoretical studies of the local structure of Cu2 + center in aluminium lead borate glasses by their EPR and optical spectra

Abstract

The local structure of the Cu2+ center in aluminium lead borate glasses was theoretically studied based on the optical spectral data and high-order perturbation formulas of the electron paramagnetic resonance (EPR) parameters (g factors g||, g⊥ and the hyperfine structure constants A||, A⊥) for a 3d9 ion in a tetragonally elongated octahedron. In the calculations, the ligand orbital and spin–orbit coupling of the impurity Cu2+ are taken into account; the required crystal-field parameters are estimated from the superposition model. Based on the calculations, the defect model of the Cu2+ center was confirmed and the defect structure (i.e., the ligand O2− octahedron around Cu2+ is determined to suffer about 19.2% relative elongation along the C4 axis due to the Jahn–Teller effect) was acquired, and a negative sign for A|| and positive sign of A⊥ for the Cu2+ center were suggested in the discussion.