Research on the g factors and tetragonal distortion of the Cu2+ tetrahedral center in ZnS : Cu2+ nanocrystals

The EPR g factors g(parallel to) and g(perpendicular to) for the tetragonal Cu2+ tetrahedral clusters in ZnS : Cu2+ nanocrystals are calculated from two theoretical methods, the complete diagonalization (of the energy matrix) method (CDM) and the perturbation theory method (PTM). Both methods are based on the cluster approach in which not only the contribution due to the spin-orbit parameter of the central metal (3d(n)) ion but also that of ligand ions via the covalence effect are considered. The calculated results from both methods are in reasonable agreement with the experimental values, suggesting that either CDM or PTM can be used to explain the g factors of d(9) ions in tetrahedral clusters. The calculations indicate that the Cu2+ tetrahedra in ZnS : Cu2+ nanocrystals are tetragonally compressed (with the ground singlet B-2(2) (vertical bar d(xy)>)) rather than tetragonally elongated. This point is consistent with the expectation based on the Jahn-Teller effect.