Xie Lin-Hua

Ligand-field treatment for the optical and electron paramagnetic resonance spectra of ZnO:V3+

In this work, a full ligand-field energy matrix (45 x 45) diagonalization treatment for 3d(2) ions in trigonal symmetry C(3v) is performed on the basis of a central metal ion-ligand covalency model including the ligand spin-orbit (SO) coupling. Optical fine structure and electron paramagnetic resonance (EPR) spectra of ZnO:V(3+) are uniformly explained.

First-principles calculations of the elastic, electronic and optical properties of AgGaS2

Density functional theory calculations using ultrasoft pseudopotentials and the generalized gradient approximation were performed to investigate the elastic, electronic and optical properties of AgGaS2 crystals with chalcopyrite structure. The optimized structure parameters are in good agreement with the experimental data. The mechanical stability of AgGaS2 is confirmed by calculations of the elastic constants. The band structure and density of states were calculated and it is shown that the crystal is a semiconductor with a direct energy band gap of about 1.005 eV for AgGaS2. Calculations of the optical properties, namely the dielectric function, refractive index, extinction coefficient, absorption coefficient, optical reflectivity and electron energy loss spectrum, were performed for the energy range 0–25 eV. The results indicate that AgGaS2 is a promising mid-IR crystal material.

Micromagnetic simulation of Sm—Co/α-Fe/Sm—Co trilayers with various angles between easy axes and the film plane

Hysteresis loops and energy products have been calculated systematically by a three-dimensional (3D) software OOMMF for Sm—Co/α-Fe/Sm—Co trilayers with various thicknesses and β, where β is the angle between the easy axis and the field applied perpendicular to the film plane. It is found that trilayers with a perpendicular anisotropy possess considerably larger coercivities and smaller remanences and energy products compared with those with an in-plane anisotropy. Increase of β leads to a fast decrease of the maximum energy product as well as the drop of both remanence and coercivity. Such a drop is much faster than that in the single-phased hard material, which can explain the significant discrepancy between the experiment and the theoretical energy products. Some modeling techniques have been utilized with spin check procedures performed, which yield results in good agreement with the one-dimensional (1D) analytical and experimental data, justifying our calculations. Further, the calculated nucleation fields according to the 3D calculations are larger than those based on the 1D model, whereas the corresponding coercivity is smaller, leading to more square hysteresis loops and better agreement between experimental data and the theory.

Unified explanation for optical and high-pressure spectra of Ni2+ ions in ZnS crystal

Abstract The optical spectra of ZnS:Ni 2+ are explained on the basis of both the complete energy matrix diagonalization procedure (CDP) and the crystal-field-like model. The calculated d–d transitions agree well with experimental data. The calculations are then extended to include the effects of pressure using the experimentally established equation of state of ZnS. The estimated pressure coefficients are also in agreement with experimental results.

Examination on the electron paramagnetic resonance spectra and the photoluminescence spectra of the Cr3+ ions in the KMgF3 crystal

Abstract In this paper, the photoluminescence spectra and the electron paramagnetic resonance spectra of the Cr 3+ ions in the KMgF 3 crystal are explained based on the complete energy matrix diagonalization procedure and a crystal–field like model. The results agree well with the experimental data. It is also shown that the nearest neighbor F − ions deviate 1.3981 and −0.486° from their original position because of the K + vacancy.