• Z H Zhang

      Articles written in Pramana – Journal of Physics

    • Investigations on the local structure and 𝑔 factors for the interstitial Ti3+ in TiO2

      L H Wei S Y Wu Z H Zhang X F Wang Y X Hu

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      The EPR 𝑔 factors $g_{i}$ $(i = x, y, z)$ for the interstitial Ti3+ in rutile are theoretically studied from the perturbation formulas of these parameters for a 3d1 ion in rhombically compressed octahedra. The ligand octahedron in the impurity center is found to be less compressed than that on the host interstitial site due to the Jahn–Teller effect. The local compression parameter $(\approx 0.026)$ and the rhombic distortion angle $\delta \phi'$ $(\approx 0.7^{\circ})$ around the impurity Ti3+ are smaller than the host values ($\approx 0.091$ and 3.5°). The theoretical 𝑔 factors based on the above local structural parameters are in good agreement with the experimental data. In addition, the 𝑔 factors for a tetragonal interstitial Ti3+ center are also reasonably interpreted.

    • Theoretical studies of the g factors and local structure for Pt3+ in 𝛼-Al2O3

      Z H Zhang S Y Wu S X Zhang L L Li

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      The anisotropic 𝑔 factors and local structure for the trigonal Pt3+ centre in 𝛼-Al2O3 are theoretically investigated from the perturbation formulas of the 𝑔 factors for a $5d^7$ ion in trigonal symmetry. The Pt3+ impurity is found to experience an outward displacement by about 0.18 Å away from the centre of the oxygen octahedron along the $C_3$-axis. The calculated g factors based on the above axial displacement show good agreement with the observed values. Importantly, the pending problem of $+3$ valence state of the doped Pt in 𝛼-Al2O3 is theoretically clarified, and the possibility of Pt+ ($5d^9$) is thus excluded in this work.

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