Calculations of the local structure and EPR parameters for Cu2 + ions in xMgO-(30 − x)Na2O-69B2O3 glasses at different composition x

The local structures and electron paramagnetic resonance (EPR) parameters as well as their composition (x) dependences for Cu2 + in xMgO·(30 − x)·Na2O·69B2O3(5 ≤ x ≤ 17 mol%) glasses are theoretically studied by analyzing these parameters for tetragonally elongated 3d9 complexes. The nonlinear variations of the EPR spectra with modifier MgO composition x can be ascribed to the approximately parabolic relationships between cubic field parameter Dq, orbital reduction factor k, local relative tetragonal elongation ratio ρ, core polarization constant κ and reduction factor H with x. The [CuO6]10 − complexes may experience the slight relative elongations of about 0.4% due to the Jahn-Teller effect. The theoretical d-d transition bands and EPR parameters for the various composition x are in good agreement with the observed results. The above composition dependences of the relevant quantities are illustrated as the modifications of the local crystal-fields and electronic states in the vicinity of the Cu2 + dopants with x.