Investigations on the EPR parameters and local structures for the substitutional Ti³⁺ and W⁵⁺ centers in stishovite

Local structures and electron paramagnetic resonance (EPR) parameters ( g factors g x , g y , and g z ) for the substitutional Ti 3+ and W 5+ centers in stishovite are theoretically investigated by using the high-order perturbation formulas of these parameters for a d 1 ion in rhombically compressed octahedra. In the calculation formulas, the related molecular orbital coefficients are obtained from the cluster approach, and the relevant crystal-field (CF) parameters are determined from the superposition model, which enables to connect these CF parameters and, hence, the studied g factors with the local structures of the Ti 3+ and W 5+ centers in stishovite. Based on the calculations, the impurity–ligand bond lengths parallel and perpendicular to the C 2 -axis are found to be R ′ || (≈1.751 and 1.717 Å) and R ′ ⊥ (≈1.788 and 1.806 Å) with the planar bond angles θ ′ (≈89.0° and 88.2°) for the studied [TiO 6 ] 9− and [WO 6 ] 7− clusters, respectively. The calculated results are in good agreement with the experimental data, and the validity of the results is discussed.