Theoretical investigations on the g factors and local structures for Cu2+ in the ZnX (X= O, S and Se) nanocrystals

Abstract

ABSTRACTThe g factors and local structures for Cu2+ in the ZnX (X = O, S and Se) nanocrystals at room temperature are theoretically investigated by the perturbation calculations for a tetragonally distorted tetrahedral 3d9 cluster in a consistent way, and the isotropic g factor is predicted for the ZnS:Cu2+ nanocrystals at room temperature. The bond angles θ between the four equivalent Cu2+−X2− bonds and the C4 axis are found to be about 1.26°, 1.24° and 1.07°, respectively, larger in the ZnO, ZnS and ZnSe nanocrystals than that (θ0 ≈ 54.74°) for an ideal tetrahedron, inducing tetragonally compressed tetrahedra. The declining tendency (ZnO > ZnS > ZnSe) of the tetragonal angular distortion Δθ (= θ − θ0) can be ascribed to the decreasing strength of the dynamic Jahn–Teller effect via the vibration interactions of the [CuX4]6− groups due to the weakening Cu2+−X2− bonding. The isotropic g factors are attributable to the appropriate Δθ due to the dynamic Jahn–Teller effect and the internal stress. The slightly increasing (ZnO < ZnS < ZnSe) g factors can be illustrated by the declining cubic field parameter Dq, angular distortion Δθ and covalency factor N of the systems.