中文摘要：

采用密度泛函理论（DFT）B3LYP，6—31G＊方法优化了一系列含有噻唑生色团的Y-型有机杂环分子的几何构型，在此基础上结合有限场（FF）方法和含时密度泛函理论（TD-DFT）对分子的非线性光学（NLO）活性和电子光谱进行计算分析．结果表明，这些分子具有A-π．D-π-A（A：受体，D：给体）结构，分子基态偶极矩、极化率和二阶NLO系数（β）随支链共轭桥的增长及生色团共轭效应的增大而增大．同时，该系列有机杂环分子的二阶极化率总的有效值（βtot）与其前线分子轨道能级相关，分子的前线分子轨道能级差越小，风值越大．

英文摘要：

Density functional theory （DPT） B3LYP/6-31G＊ method was employed to optimize the structures of a series of Y-shaped organic heterocyclic molecules containing a thiazole chromophore. Based on the obtained stable molecular configuration, we adopted the finite field （FF） method and time-dependent density-functional theory （TD- DFT） to calculate and analyze the nonlinear optical （NLO） properties and electric spectra of these molecules. Results show that the molecules possess A-π.D-π-A（A： acceptor, D： donor） structures, and the dipole moment of the ground state, the polarizability, and the second-order NLO coefficient （β） of the molecules increase with increase of the length of conjugate bridge of the branched chain and the conjugation effect of the chromophore. The total virtual value of second-order polarizability （βtot ） of the series of organic heterocyclic molecules was found to be related to the energy gap of the frontier molecular orbital. The molecule with smaller energy gap of the frontier molecular orbital shows larger values of βtot.