材料期刊网

The defect structure and the EPR parameters (the g factors, the hyperfine structure constants and the superhyperfine parameters) for the tetragonal Ir(2+) center in AgBr are theoretically investigated using the perturbation formulas of these parameters for a 5d(7) ion in tetragonally elongated octahedra. In the calculations, the contributions from the ligand orbital and spin-orbit coupling interactions and the local lattice (elongation) distortion due to the Jahn-Teller effect are taken into account. Related molecular orbital coefficients and the ligand unpaired spin densities are determined quantitatively using a cluster approach. The impurity center is attributed to the substitutional [IrBr(6)](4-) cluster on host Ag(+) site, which suffers the relative elongation of about 0.08 angstrom along C(4) axis due to the Jahn-Teller effect. The calculated EPR parameters based on the above Jahn-Teller elongation show good agreement with the observed values.