Laboratoire de Chimie et de Physique Quantiques, IRSAMC/UMR5626, Université de Toulouse 3, 118 Route de Narbonne, Toulouse Cédex 4 F-31062, France.
J Chem Phys. 2010 Aug 28;133(8):084307. doi: 10.1063/1.3480014.
The zero-field splitting (ZFS) of a model monometallic Mn(III) complex is theoretically studied as function of a systematic symmetry lowering. First, we treat the octahedral case for which the standard S.D.S model Hamiltonian cannot be applied due to a zero-field splitting in the absence of anisotropy induced by the spin-orbit coupling between the two spatial components of the (5)E(g) state at second-order of perturbation. Next, the symmetry is lowered to D(4h) and D(2h) and the anisotropic spin Hamiltonian is extracted using effective Hamiltonian theory. A simple relation is derived between the ratio E//D/ and the applied rhombic and axial distortions. Moreover, it is shown that close to O(h) symmetry, the orbital mixing due to spin-orbit coupling can be accurately described with Stevens fourth-order operators. The calculated tendencies are interpreted within a refined Racah plus ligand field model and it is shown that the ZFS parameters in Mn(III) complexes follow special rules that are nonintuitive compared to other d(n) configurations. Finally, some angular distortions are applied to study their effect on the anisotropy.
理论研究了模型单核 Mn(III)配合物的零场分裂（ZFS）作为系统对称性降低的函数。首先，我们处理八面体情况，由于自旋轨道耦合在二阶微扰下在没有各向异性的情况下在两个（5）E(g)态的空间分量之间诱导的零场分裂，标准 S.D.S 模型哈密顿量不能应用。接下来，对称性降低到 D(4h)和 D(2h)，并使用有效哈密顿理论提取各向异性自旋哈密顿量。推导出 E//D/与施加的斜方和轴向畸变之间的简单关系。此外，还表明，在接近 O(h)对称性的情况下，由于自旋轨道耦合引起的轨道混合可以用史蒂文斯四阶算符准确地描述。计算趋势在改进的 Racah 加配体场模型中进行了解释，并表明 Mn(III)配合物中的 ZFS 参数遵循特殊规则，与其他 d(n)构型相比，这些规则是直观的。最后，应用一些角度畸变来研究它们对各向异性的影响。
