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

Abstract

The EPR g factors g∥ and g⊥ 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 (3dn) 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 d9 ions in tetrahedral clusters. The calculations indicate that the Cu2+ tetrahedra in ZnS:Cu2+ nanocrystals are tetragonally compressed (with the ground singlet 2B2 ()) rather than tetragonally elongated. This point is consistent with the expectation based on the Jahn–Teller effect.

Research on the optical band positions, spin-Hamiltonian parameters and atom-position parameter of Co2+ ion in CdSe crystal

“…[21,22], where γ¼t or e indicates the irreducible representation of T d group. N γ (the normalization coefficients) and λ β (β ¼s or π, the orbital mixing coefficient) are the MO coefficients.…”

“…However, for CdSe: Co 2 þ , since the spin-orbit parameter p 0 ζ ( E1659 cm À 1 [19]) of free ligand ion Se 2 À is larger than that ( p 0 ζ E 533 cm À 1 [20]) of free central ion Co 2 þ , the contributions from the spin-orbit parameter of ligand ion via covalence effect should be contained. Thus, a two-spinorbit-parameter model (where the contributions due to spin-orbit parameters of both the central d n ion and ligand ion are considered [18,21,22]) ought to be applied. The present work is intended to give a unified calculation of optical and EPR data for the Co 2 þ -doped CdSe with the CDM based on the two-spin-orbitparameter model.…”