Zhao Min-Guang

A μ-κ-α correlation ligand-field model for the Ni2+-6X- cluster

The dipole moment-covalency-polarisability correlation ligand-field model is proposed, after a number of experimental spectra data have been analysed. In this model, once the mu - kappa - alpha correlations are established, there is no need to introduce the fitting parameters in order to investigate the optical and magnetic properties for a set of Ni2+-6X- clusters. Using this model and a parametrisation d-orbit theory, the theoretical absorption spectra of Ni2+-6X- clusters, such as RbNiF3, KNiF3, NiF2, BaNiF4, RbNiCl3, CsNiCl3, NiCl2, (CH3)4NNiCl3, CsNiBr3, NiBr2, (CH3)4NNiBr3, RbNiBr3, CsNiI3 and NiI2 are calculated without any fitting parameters. The calculation results agree well with the experimental findings. The calculated absorption spectra, EPR parameters and magnetic susceptibility are in good agreement with experimental results, in particular for CsNiCl3.

The eighth-order perturbation formula for the EPR cubic zero-field splitting parameter of d5(6S) ion and its applications to MgO:Mn2+ and MnCl2.2H2O

The eighth-order perturbation formula for the EPR cubic field splitting parameter alpha has been obtained by taking a cubic crystal field and the spin-orbit interaction as the perturbation Hamiltonian. In the calculation, not only spin quartet states but also spin doublet states have been considered. The calculated result shows that the contributions of the double states and eighth-order perturbation cannot be neglected. For MgO:Mn2+ and MnCl2.2H2O, the d-d transitions and the cubic zero-field splitting parameter have been calculated by using Zhaos self-consistent-field (SCF) orbital for the Mn2+ ion and the high-order perturbation formula for the cubic zero-field splitting parameter have been obtained. The results of applications agree well with experiments.

The study of the optical and the EPR spectra of V+4 in zircon-type crystals

Abstract It has been believed that the optical and the EPR spectra of V +4 in zircon-type crystals could not be accounted for by conventional crystal field theory In the present article, this problem is analyzed and a calculation is carried out by using a superposition model The results obtained in the present study are in agreement with the experiment. Now the spectra can be explained reasonably.

Determination of the MnF2 and ZnF2 crystal structure from the EPR and optical measurements of Mn2

The authors calculate the crystalline parameters for MnF2 and ZnF2 from EPR and optical measurements on Mn2+ ions. The results support the structure data previously reported by Stout and Reed (1954) rather than that by Baur (1958). In addition, the fourth-order perturbation formulae for the EPR parameters D and E are derived.

Giant Quenching of Spin-Orbit Interaction of Ga1-xVxP Crystals

We prove the presence of a giant quenching of the spin-orbit coupling of V 2+ ion in GaP on the basis of a trigonal crystal field model and a complete diagonalization procedure. The calculated result is in good agreement with the experimental data of the thermally detected electron paramagnetic resonance. It was also shown that the dynamical Jahn–Teller explanation cannot be excluded.

High-order perturbation formulae for the zero-field splitting of a 6S ion in C3 symmetry and its application to Mn(I):Ca5(PO4)3F

The relationship between the zero-field splitting parameter D and the C3 crystalline potential components for 6S ions is established with the use of the high-order perturbation method. It is found that the effect of the spin-spin interaction within the d5 configuration is comparable with the mechanism suggested by Orbach et al. (1962). By using the d-orbital theory proposed by Zhao et al. (1982, 1983, 1984) the optical levels and the zero-field splitting of Mn(I):Ca5(PO4)3F are calculated. The results agree well with the values measured experimentally.

Zero-field splitting of tetrahedral Co2+ in the trigonal crystal field

A new high-order perturbation formula for the zero-field splitting of the 4A2 ground state of d3,7 ions in a trigonal field is derived on the basis of the weak-field approximation. The formula obtained is shown to be a good approximation for the cases where the cubic field parameter Dq is less than the Racah electrostatic parameter B and is thus especially suitable for tetrahedral Co2+ complexes. By using it, the zero-field splitting of ZnO:Co2+ is calculated from a parametrised d orbit and the parameters are determined from the optical spectra. The result agrees well with the experimental finding.

A study of the structure of the Cr3+-vacancy centre in MgO using EPR and optical spectra

The relationships among the structure parameter of the Cr3+-vacancy centre, the EPR parameter D and the splitting Delta E(2E) of the 2E state in MgO:Cr3+ are established according to third-order perturbation formulae and the SCF d orbit of a Cr3+ ion. By using these, the structure parameter of the Cr3+-Vc centre is determined quantitatively from the EPR and optical spectra data, and the results show that the displacement Delta R of the anion O2- along the (001) axis is Delta R=0.056+or-0.004 AA. This method would be effective in determining the structure parameter of other Mn+-Vc centres.

Sharp phonon modes in the high-temperature superconducting compound Y0.9Ba0.6CuO3-y

In addition to the lines appearing in the IR absorption spectra of the pure compounds Y2O3, BaCo3 and CuO and having chemical shifts, six new modes are found in the IR spectrum of the constituted superconducting samples of Y0.9Ba0.6CuO3-y in the range 400-700 cm-1. These new modes, however, disappear in the IR spectrum of nonsuperconducting samples. This seems to support the electron-phonon mechanism.

Determination of the temperature variation of the crystal structure of CdCl2 from the EPR data for Mn2

The d-orbit theory and high-order expressions for the zero-field splitting in trigonal symmetry are used to analyse the temperature variation of the crystal structure of CdCl2 using the experimental EPR data for Mn2+:CdCl2 at different temperatures. The dimension c of the hexagonal unit cell varies linearly with temperature at different rates below and above T0=375+or-10K at which the structure forms a regular octahedron. An accurate value u=0.2435(2) is obtained, which is consistent with the observed value u=0.25(1). Further accurate X-ray measurements are required for testing the results obtained.