Theoretical study of the electron paramagnetic resonance parameters and local structure for the tetragonal Ir2+ centre in NaCl

Abstract

The electron paramagnetic resonance (EPR) parameters (the g factors, hyperfine structure constants and the superhyperfine parameters) for the tetragonal Ir 2+ centre in NaCl are theoretically investigated from the perturbation formulas of these parameters for a 5d 7 ion in tetragonally elongated octahedra. This impurity centre is attributed to the substitutional [IrCl 6] 4− cluster on host Na + site, associated with the 4% relative elongation along the C4-axis due to the Jahn-Teller effect. Despite the ionicity of host NaCl, the [IrCl 6] 4− cluster still exhibits moderate covalency and then the ligand orbital and spin-orbit coupling contributions should be taken into account. In addition, the theoretical EPR parameters based on the Jahn-Teller elongation show good agreement with the observed values.