中文摘要：

采用密度泛函理论（DFT）方法,计算并分析了四氟取代十二顶点碳硼烷及其衍生物的结构和非线性光学（NLO）性质.结果表明,改变四氟碳硼烷取代基的共轭性或给吸电子能力,会使分子中碳硼笼原子间距离发生改变.碳硼烷取代基的给吸电子能力越强,其偶极矩越大.分子极化率随取代基共轭性和体积的增加而增大.引入强吸电子基或增加四氟碳硼烷取代基的共轭性,可使其二阶NLO响应明显增强.通过分析分子的电子光谱和对应的分子轨道组成可知,第一超极化率最大的分子4a＇发生碳硼笼到并苯取代基的电荷转移.

英文摘要：

The structures and second-order nonlinear optical（ NLO） properties of tetrafluoro carborane and its derivatives were investigated with density functional theory method. The results indicate that elongating the conjugation or enhancing the strength of donor（ D） and acceptor（ A） groups affect the distances of the carborane cage. Generally speaking,the dipole moment of molecule is determined by the D /A strengths,that is,the stronger D /A groups the larger dipole moment. Meanwhile,the polarizability of each molecule increases with the increasing of the conjugation and volume of substituents. Introducing the substituents with strong electron-withdrawing abilities or promoting the conjugation of substituents can effectively improve the second-order NLO coefficients. Furthermore,from the analysis of electronic absorption spectrum and the corresponding molecular orbit compositions,charge transfer pattern that comes from the carborane cage to the acene substituent illustrates the first hyperpolarizability value of molecule 4a＇ is the largest.