环蕃分子及其衍生物非线性光学性质的理论研究

采用密度泛函理论计算方法研究了环蕃分子及其衍生物的非线性光学性质，探讨了将其作为非线性光学开关材料的可能性。计算结果表明:当不施加外电场时，该新型分子和设计的衍生物分子均为中心对称结构，其非线性光学响应性质中的第一超极化率为零，对应于分子开关中的“关”状态；而在恰当的外电场强度下，转变为非中心对称结构，并具有很大的第一超极化率，对应于分子开关中的“开”状态。在电场强度小于1.39×1010 V/m时，环蕃分子及其衍生物均表现出很好的几何结构和电子结构的稳定性，虽然衍生物分子存在一个因对称性变化导致的较小的结构参数的突变，但不影响分子总体结构的稳定性。该研究从理论上证明了环蕃分子及其衍生物均可以作为非线性光学开关材料，为非线性光学材料的设计提供了理论参考。

A Theoretical Study on the Nonlinear Optical Properties of Cyclophane and Its Derivatives

The density functional theory-based computational method is used to study the nonlinear optical properties of cyclophane and its derivatives and the possibility of their use for optical switch. According to the calculation results, the new molecules have a structure of inversion center symmetry in the absence of external electrical field applied and their first hyperpolaorizability is zero, corresponding to the "off" state of the optical switch. When the external electrical field is applied, the molecules convert to structures of non-inversion center symmetry and have large first hyperpolaorizabilities, corresponding to the "on" state of the optical switch. When the electric field strength is less than 1.39×1010 V/m, cyclophane and its derivatives exhibit good stability in both geometrical structure and electronic structure. Although there exists a small change of structural parameter for cyclophane derivatives caused by broken symmetry, it does not affect its structural stability. It is proved that cyclophane and its derivatives can be used for making nonlinear optical switch and a theoretical reference for nonlinear optical materiel design is provided.