Calculations with the two-mechanism model for the spin-Hamiltonian parameters of Mo5 + ions in phosphate glasses

Abstract

The high-order perturbation formulas based on the two-mechanism model are used to calculate the spin-Hamiltonian parameters (g factors g//, g⊥ and hyperfine structure constants A//, A⊥) of the tetragonal Mo5+ centers in phosphate glasses xMoO2·(100−x)[2P2O5·Na2O]. In the calculations, not only the crystal-field (CF) mechanism concerning CF excited states in the widely-applied CF theory, but also the charge-transfer (CT) mechanism concerning CT excited states (which is often omitted) is taken into account. The calculated results are close to the experimental values. The calculations show that the contributions ΔgiCT (=gi−ge, where ge≈2.0023) and Ai(2)CT due to CT mechanism in sign are contrary to the corresponding ΔgiCF and Ai(2)CF due to CF mechanism, and the values of relative importance |QCT/QCF| of CT mechanism are about 19%, 17%, 8% and 13% for Q=Δg//, Δg⊥, A//(2) and A⊥(2). It appears that in the complete and exact calculations of spin-Hamiltonian parameters for the high valence state dn ions (e.g., Mo5+ considered here) in crystals, one should take into account the two (CF and CT)-mechanism model.