过渡金属类立方烷原子簇化合物电子结构和二阶非线性光学性质的密度泛函理论研究

Electronic Structure and Second-order NLO Properties of Cubane-like Transition Metal Cluster Compounds: A Density Functional Theory Study

采用基于第一原理的含时密度泛函理论(TDDFT)对一系列具有类立方烷簇芯结构的过渡金属簇合物二阶非线性光学性质进行了研究。结果证明, 由于簇芯结构的对称性的影响, 这一类簇分子的二阶非线性光学系数的数值要小于三核欠完整类立方烷体系。通过对电子结构的分析, 发现二阶非线性光学性质主要是由簇芯内电荷的迁移造成的。轨道分析显示, -S原子对于电荷的迁移起主要的传递作用。定域化轨道分析证明簇分子中存在的多中心键有利于簇芯内电荷的迁移。分子模拟的研究表明:虽然类立方烷结构簇分子的值比较小, 但是通过合理的配体设计, 获得具有较大值非线性光学晶体是可能的。

The time-dependent density functional theory method has been applied to study the electronic structure and second-order nonlinear optical (NLO) properties of some tetranuclear cubane-like transition metal clusters which show little second-order polarizabilities beta values due to their symmetric structure. We think the second-order NLO property comes from the charge transfer inside the cluster core, and mu-S atoms display an important role in this charge transfer, to which the multi-central bonding in these clusters is feasible. The analysis of the frontier molecular orbitals and Mulliken charge populations gave the same conclusion. Though cubane-like clusters show little beta values, our calculations indicate that it is possible to obtain NLO crystals with large beta values by further appropriate molecular design.