Papers by Author: Min Quan Kuang

Abstract: The Knight shifts and hyperfine structure constants of Tl₂Ba₂CuO_6+y are theoretically studied from the high order perturbation formulas of these quantities for a tetragonally elongated octahedral 3d⁹ cluster. The calculation results reveal good agreement with the observed values. The obvious anisotropies of the Knight shifts can be ascribed to the local tetragonal elongation of the Cu²⁺ site. The results and the local structure of the system are discussed.

Abstract: The g factors for the cubic Fe⁺ centers in LiF and NaF are theoretically investigated from the perturbation formula of the g factor for an octahedral 3d⁷ cluster including the contributions from the ligand orbital and spin-orbit coupling interactions. The increasing order of the g factor (i.e., LiF < NaF) can be ascribed to the decrease in covalency and the strength of cubic crystal-field of the systems. The validity of the results is discussed.

Abstract: The spin Hamiltonian parameters (g factors and the hyperfine structure constants) for the octahedral interstitial Fe⁰ and Mn in silicon are theoretically investigated using the perturbation formulas of these parameters for a 3d⁸ ion under octahedral environments based on the cluster approach. The theoretical results show good agreement with the experimental data, and the ligand contributions should be considered due to the strong covalency of the systems. The interstitial occupation of the above novel 3d⁸ impurities of rare valence states in silicon is discussed.

Abstract: The Spin Hamiltonian Parameters (the G Factors and the Superhyperfine Parameters) for the Tetragonal [Fe(CN)₄Cl₂]^5- Complex in Nacl Are Theoretically Investigated from the Perturbation Formulas of these Parameters for a Low Spin (S=1/2) 3d⁷ Ion in Tetragonally Elongated Octahedra. this Impurity Center Is Attributed to the Substitutional Fe²⁺ (in the Form of [Fe(CN)₆]^4–) on Host Na+ Site Reduced by Capturing One Electron during the X-Ray Irradiation Process, with the Two Axial Ligands CN– Replaced by Two Cl–. since the Crystal Fields of the Axial Ligands Cl– Are Weaker than those of the Perpendicular Ligands CN–, the [Fe(CN)₄Cl₂]^5- Complex Exhibits a Tetragonally Elongated Octahedron. this System Shows the Low Spin S=1/2 of the Strong Crystal Field Case, which Is Unlike the High Spin S=3/2 of the Weak and Intermediate Crystal Field Case for Fe⁺ in Conventional Chlorides. the Theoretical Spin Hamiltonian Parameters Are in Reasonable Agreement with the Experimental Data, and the Results Are Discussed.

Abstract: The EPR parameters and the local structure for Co2+ in ZnO are deduced from the perturbation formulas of these parameters for a 3d7 ion in a trigonally distorted tetrahedron. The ligand orbital and spin-orbit coupling contributions are taken into account uniformly from the cluster approach in view of the covalency of the system. The impurity V3+ is found not to locate exactly on the Zn2+ site but to experience a small displacement of 0.04 Ǻ away from the ligand triangle, along the C3 axis. The theoretical EPR parameters based upon the above impurity displacement are in good agreement with the observed values.

Abstract: The electron paramagnetic resonance parameters (g-factors and the hyperfine structure constants) for the Cu2+ center in lanthanum magnesium nitrate (LMN) are theoretically studied from the conventional perturbation formulas of these parameters for a 3d9 ion in tetragonally elongated octahedra. The studied complex is found to exhibit the slight tetragonal elongation (characterized by the relative elongation ratio ρ  4%) due to the Jahn-Teller effect, which may entirely conceal the original trigonal distortion of the host Mg2+ site in LMN. The conventional formulas containing only the metal orbital and spin-orbit coupling contributions are proved to be valid for the Cu2+ center in view of the weak covalency and ligand spin-orbit coupling interactions. This defect is also compared with the similar Cu2+ center of the Jahn-Teller nature on the octahedral interstitial site in the CdSe nanocrystals.