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近年来实验发现,通过化学键调整分子间空间取向可以提高其非线性光学(NLO)响应系数。本文以对硝基苯酚分子为单体,利用化学键将两个单体连接得到一系列二聚体分子,用量子化学方法计算了它们的分子一阶超极化率(β)。研究表明,二聚体分子的β值与单体间距离和连接方式有关,在一定距离时出现极大值;而且,此类分子的β值具有显著的溶剂效应,但与单体间距离的依赖关系和气相中相同。由此可见,通过化学键改变单体间距离和连接方式可以作为提高有机分子NLO响应系数的有效途径。
In recent years, it has been found experimentally that the nonlinear optical (NLO) response coefficient can be improved by adjusting the spatial orientation of molecules by chemical bonds. In this paper, p-nitrophenol molecules are used as monomers, and a series of dimeric molecules are obtained by connecting two monomers by chemical bonds. Their first order hyperpolarizabilities (β) are calculated by quantum chemistry method. The results show that the β value of dimeric molecule is related to the distance and connection between monomers, and the maximum value appears at a certain distance. Moreover, β value of these molecules has significant solvent effect, Dependency is the same as in the gas phase. Thus, chemical bonding can be used as an effective way to improve the NLO response coefficient of organic molecules by changing the distance and connection between monomers.