Rui-Peng Chai

Theoretical study of the dependence of EPR spectra on local structure for octahedral Cr(3+) centres in oxides and fluorides series

A theoretical method for investigating the inter-relation between the EPR parameters and local structure has been established on the basis of the complete energy matrices for 3d3 configuration ions in both the trigonal and tetragonal ligand fields. By means of this method, the local structure of the octahedral Cr3+ centres in double molybdates series and spinels series as well as the perovskite-type fluorides series has been studied systematically. Furthermore, the dependence of the EPR zero-field splitting parameter D on the local structure parameters in both trigonal and tetragonal ligand-fields has been revealed, simultaneously. The inter-relation between the EPR parameters D and Δg(g //  − g ⊥) is also elucidated.

Theoretical studies of EPR spectra and defect structure for Er3+ center in lithium niobate

The optical and EPR spectra of octahedral Er(3+) center in LiNbO(3) have been studied by diagonalizing 364 x 364 complete energy matrices. The new set of crystal-field parameters that can well account for the Stark levels and EPR parameters have been obtained for Er(3+) ions in LiNbO(3). Simultaneously, by simulating the most reliable six-order parameter B(60) obtained, we have presented the evidence that the Er(3+) ions do not occupy the actual Li(+) site, but have a displacement along the C(3)-axis away from the Li(+) center by about 0.0454 nm. The conclusion is well in accord with that drawn by earlier workers.

Theoretical investigations of the local structure distortion and relationship between the EPR parameter and spin-orbit coupling coefficients for CsCdX3:Ni2+ (X = Cl, Br) systems

The EPR zero-field splitting parameters and structural distortion of Ni2+-doped CsCdX3 (X = Cl, Br) systems have been studied on the basic of 45f × 45 complete energy matrices for a configuration ion in trigonal ligand field, in which the contributions from the spin-orbit coupling coefficients of the central ions and ligands are taken into account simultaneously. It is shown that the local structure exhibits compression distortions for CsCdX3 (X = Cl, Br):Ni2+ systems, and the contribution from the s.o. coupling coefficient of ligands to the covalent effect should not be neglected. Simultaneously, the relationship between the EPR parameter D and the spin-orbit coupling coefficients (ζ, ) as well as the average parameter ζ1( ) and the divergent parameter ζ2( ) have been discussed.

Theoretical Investigations of the Local Structure Distortion and EPR Parameter for Ni2+-doped Perovskite Fluorides

By analyzing the optical spectra and electron paramagnetic resonance parameter D, the local structure distortion of (NiF6)4− clusters in AMF3 (A=K, Rb; M=Zn, Cd, Ca) and K2ZnF4 series are studied using the complete energy matrix based on the double spin-orbit coupling parameter model for configuration ions in a tetragonal ligand field. The results indicate that the contribution of ligand to spin-orbit coupling interaction should be considered for our studied systems. Moreover, the relationships between D and the spin-obit coupling coefficients as well as the average parameter and the divergent parameter are discussed.

The defect structure and EPR parameters for Er3+ in molybdates: a complete energy matrices study

In this paper, we develop a complete energy matrices approach investigating the defect structure and EPR parameters ( , , and ) for Er3+ in molybdates. In this approach, the crystal-field parameters used in the calculations are determined from the superposition model and the structural data for tetragonal distortion. The local distortion angles Δθ = −1.628°, Δθ = −1.843° and Δθ = −2.874° are obtained for Er3+ in SrMoO4, PbMoO4 and CaMoO4 crystals, respectively. Moreover, the influence of the orbital reduction factor k and the local distortion angle Δθ on the EPR parameters is analyzed.

Phase Transition Properties of a Ferroelectric Superlattice with Surface Modification

The phase diagrams of a ferroelectric superlattice with finite alternating layers are investigated by using the transverse Ising model within the mean-field approximation. The effects of surface modification are introduced through a surface exchange interaction constant and a surface transverse field parameter. The results indicate that the features of the phase diagrams can be greatly modified by changing the transverse Ising model parameters. In addition, the crossover features of the inside transverse field parameters from the ferroelectric dominant phase diagram to the paraelectric dominant phase diagram are determined for a finite alternating superlattice.