Interpretation of the EPR parameters through investigating the local lattice deformations for the two Pt3+ centers in ZnWO4

The local lattice distortions and the electron paramagnetic resonance (EPR) parameters (anisotropic g factors and the hyperfine structure constants) for the two Pt³⁺ centers in ZnWO₄ are theoretically investigated by utilizing the perturbation formulas of these parameters for a 5d ⁷ ion under rhombically elongated and compressed octahedra. The elongated (and compressed) centers are ascribed to the PtO₆]^9? clusters on Zn²⁺ site suffering the axial elongation of 0.01 Å (and compression of 0.02 Å) along Z axis and the planar bond angle variations of 7.4° (and 7.8°), respectively, due to the Jahn–Teller effect. The above local lattice deformations may considerably cancel the original large axial elongation (~0.31 Å) and perpendicular rhombic angular distortion of the host ZnO₆]^10? cluster and yield more regular PtO₆]^9? clusters in the impurity centers. The calculated EPR parameters based on the above lattice deformations show good agreement with the experimental data, and the local structures of the impurity centers are discussed.