Du Mao-Lu

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.

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.

Theoretical studies on the EPR of K3Co(CN)6: Cr3+

Abstract The high order perturbation formulae of the EPR parameters possessing C2; symmetry for the d3 ion in the ground state are derived and applied to the study of the high pressure effect on K3Co(CN)6:Cr3+. The calculated results agree well with the experimental findings. It is hoped that the equations for V − P and φ − P will be tested by further X-ray diffraction experiments.

Determination of the state equation of NiX2 from the high-pressure spectra shifts

The high-pressure state equation and alpha -P correlation of NiX2(X identical to F, Cl, Br, or I) are determined from the pressure spectra shifts of NiCl2 and NiBr2 based on the mu kappa alpha model. By using the state equation and alpha -P correlation the pressure behaviours of NiF2 and NiI2 are predicted.