Theoretical Studies on the Local Structure and Electron Paramagnetic Resonance Parameters for Cu2+ Centers in TiO2 with one Oxygen Vacancy Adjacent

Based on the defect model that the impurity Cu²⁺ in TiO₂ on the octahedral Ti⁴⁺ site is associated with one oxygen vacancy VO along the C₂ axis, the electron paramagnetic resonance (EPR) parameters, i. e., the g factors gi (i = x;y; z) and the hyperfine structure constants At, of the Cu²⁺-VOcenter in TiO2 are calculated by using the perturbation formulas of these parameters for a 3d⁹ ion in a rhombically elongated octahedra. From this study, the impurity Cu²⁺ is found to be away from VO by a distance Dz (≈ 0:33 Å) along the C2 axis, meanwhile the four O^2- ions in the plane perpendicular to the C2 axis may be shifted by Dx (≈ 0:28 Å) towards VO due to the electrostatic interaction between these ions and VO. The theoretical results based on the above local structure distortions show good agreement with the experimental data.