Theoretical studies of the concentration dependences of d-d transition band, g factors, and local distortion for V4+ in Li2 O-PbO-B2 O3 -P2 O5 glasses

Abstract

In this work, the g factors, d-d transition band, local distortion, and their concentration dependences for impurity V⁴⁺ in 20Li₂ O-20PbO-45B₂ O₃ -(15 - x)P₂ O₅ :V₂ O₅ (0 ≤ x ≤ 2.5 mol%) glasses are theoretically investigated by using perturbation formulas of g factors for a tetragonally compressed octahedral 3d¹ cluster. In the light of the cubic polynomial concentration functions for cubic field parameter D_q , covalency factor N, and relative tetragonal compression ratio ρ, the calculated concentration dependences of d-d transition band and g factors for V⁴⁺ show good agreement with the experimental data. With increasing x, N (≈0.7682-0.8165) displays the monotonously increasing trend, whereas ρ (≈6.5-4.2%) and D_q (≈1504.9-1481.1 cm^-1 ) exhibit the decreasing tendencies. The above concentration dependences can be ascribed to the modifications of the V⁴⁺ -O^2- bonding and orbital admixtures around the impurity V⁴⁺ due to the effects of V₂ O₅ doping on the stability of the glass network, the strength of local crystal fields, and the electron cloud distribution.

Keywords: Jahn-Teller effect; Li2O-PbO-B2O3-P2O5 glasses; V4+; ligand field theory; spin Hamiltonian theory.