A Theoretical Study of Concentration-Dependent Xcaf2-20Teo2-(79‒x)na2b4o7-cuo Glass: Local Distortions, EPR Parameters and Optical Properties

The electron paramagnetic resonance parameters (EPR) and local structure properties of the Cu2+ center in xCaF2–20TeO2-(79-x)Na2B4O7-CuO glasses are theoretically studied based on the high-order perturbation formulae of a 3d9 ion in a tetragonally elongated octahedron. Determined from the best fitted piecewise linear function (the reverse point at 40 mol%), the corresponding overall varying tendencies and fluctuations of local distortions, EPR parameters and optical properties are reproduced, which can be ascribed to the generated non-bridging oxygen's. The microscopic mechanisms of the above concentration dependences for these quantities are illustrated from the transformation of BO3 and TeO3 units. Meanwhile, the electronic properties are obtained through the covalence parameters N and the decrease optical basicity, which both mean the decreasing covalency of the whole glass systems and strong ionicity around Cu2+.