Wu Shao-Yi, Dong Hui-Ning, Gao Xiu-Ying
Department of Applied Physics, University of Electronic Science and Technology of China, College of Physical Electronics, Chengdu 610054, PR China.
Spectrochim Acta A Mol Biomol Spectrosc. 2006 Mar 1;63(3):749-53. doi: 10.1016/j.saa.2005.06.029. Epub 2006 Feb 3.
The spin Hamiltonian (SH) parameters (zero-field splitting D and anisotropic g factors g(||) and g( perpendicular)) and local structures for Cs(3)CoX(5) (X = Cl, Br) are theoretically studied from the perturbation formulas of the SH parameters for a 3d(7) ion in tetragonally distorted tetrahedra based on the cluster approach. In these formulas, both the contributions from the crystal-field (CF) mechanism and those from the charge-transfer (CT) mechanism are taken into account. It is found that the CoX(4) clusters are slightly elongated and the tetragonal distortion angles Deltatheta(=theta-theta(0), where theta(0) equals to approximately 54.74 degrees is the bonding angle related to the C(4)-axis in regular tetrahedra) are about -1.68 degrees and -1.71 degrees for X = Cl and Br, respectively. The calculated SH parameters as well as the effective magnetic moments based on the above angles are in reasonable agreement with the observed values. From the studies, the importance of the contributions to the SH parameters from the CT mechanism increases with increasing the spin-orbit coupling coefficient of the ligand, i.e., Cl(-) < Br(-). The results are compared with those obtained from the conventional crystal-field model in the previous works.
基于团簇方法，从四方畸变四面体中3d⁷离子的自旋哈密顿量（SH）参数的微扰公式出发，对Cs₃CoX₅（X = Cl，Br）的SH参数（零场分裂D和各向异性g因子g(||)和g(⊥)）及局部结构进行了理论研究。在这些公式中，同时考虑了晶体场（CF）机制和电荷转移（CT）机制的贡献。结果发现，[CoX₄]²⁻团簇略有拉长，对于X = Cl和Br，四方畸变角Δθ（=θ - θ₀，其中θ₀约等于54.74°是正四面体中与C₄轴相关的键角）分别约为 -1.68°和 -1.71°。基于上述角度计算得到的SH参数以及有效磁矩与观测值合理吻合。研究表明，CT机制对SH参数的贡献重要性随着配体自旋 - 轨道耦合系数的增加而增大，即Cl⁻ < Br⁻。将结果与先前工作中从传统晶体场模型获得的结果进行了比较。
