含不同共轭桥的TCNQ 开闭壳层体系NLO 性质的DFT 研究DFT Study.PDF

2010 年第 68 卷 化 学 学 报 Vol. 68, 2010 第 24 期, 2509～2515 ACTA CHIMICA SINICA No. 24, 2509～2515 ·研究论文· 含不同共轭桥的 TCNQ 开闭壳层体系 NLO 性质的 DFT 研究 刘海波 仇永清* 孙世玲 刘春光 孙晓娜 (东北师范大学化学学院 功能材料化学研究所 长春 130024) 摘要 采用密度泛函理论(DFT)结合有限场(FF)方法, 对不同共轭桥连接的四氰代二甲基苯醌(TCNQ)开壳层和闭壳层 电子态的非线性光学(NLO)系数进行计算, 并以乙烯桥为例讨论共轭链长度与 NLO 性质的关系. 结果表明: 开壳层体 系的极化率和二阶超极化率值都大于闭壳层体系, 且共轭桥的共轭性越强, 体系的极化率和二阶超极化率越大; 在自 由基体系中, 单重态的二阶超极化率随双自由基成分 y 和自旋多重度的增加而增大. 体系的共轭链增长, BLA (Bond Length Alternation, 共轭分子中相邻单、双键键长差的平均值)逐渐减小, 双自由基成分 y 逐渐增大, 体系的二阶超极化 率也逐渐增大. 关键词 双自由基; 自旋多重度; NLO 性质 DFT Study on Nonlinear Optical Properties of Open and Closed Shell Systems of TCNQ Involving Different Conjugation Bridges Liu, Haibo Qiu, Yongqing* Sun, Shiling Liu, Chunguang Sun, Xiaona (Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Changchun 130024) Abstract Nonlinear optical coefficients of the closed and open shell systems of TCNQ connecting differ- ent conjugation bridges were computed by using density functional theory (DFT) combining with the finite field (FF) approach. Take the ethylene for an example to discuss the relationship between conjugation length and the NLO properties. The results show that the polarizability and second hyperpolarizability values of open shell systems are larger than those of closed shell systems. Moreover, the polarizabilities and second hyperpolarizabilities become large with the increased conjugation of the conjugation bridge. For the diradi-