超价化合物F_nLi_(n+1)(n=1～3)一阶超极化率的理论研究

Theoretical Study on Static First Hyperpolarizabilities of Hypervalent Compounds F_nLi_(n+1)(n=1—3)

采用UMP2/6-311+G(3df)方法得到了FnLin+1(n=1～3)体系的8个全部实频的异构体构型,并研究了这些体系的非线性光学性质.结果表明,这类超价化合物具有较大的一阶超极化率值(β0=2299.2～12322.3a.u.).超价化合物中弥散的电子云使体系具有较低的跃迁能,从而决定了FnLin+1具有较大的一阶超极化率.提示非中心对称的超价化合物将是一类潜在的非线性光学分子.

Using the UMP2 /6-311 ＋ G（ 3df） method,eight optimized structures of FnLin＋1（ n = 1—3） with all real frequencies were obtained. The nonlinear optical（ NLO） properties of the species were investigated. The results show that the hypervalent compounds have large first hyperpolarizabilities with β0 = 2299. 2—12322. 3 a. u. . It is found that the diffusive electron clouds of hypervalent compounds play very important roles in low excited energies,which results in large first hyperpolarizabilities of FnLin＋1. The present investigation indicates that the noncentro-symmetric hypervalent compound is a new kind of potential NLO molecules.