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 Ai, 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 ∆z (≈ 0.33 Å) along the C2 axis, meanwhile the four O2− ions in the plane perpendicular to the C2 axis may be shifted by ∆x (≈ 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.