含氟炔基三苯液晶分子太赫兹吸收的计算模拟研究

Simulation on terahertz absorption of fluorinated phenylacetylene biphenyl liquid crystal molecules

以密度泛函理论为基础,利用Gaussian09程序包,通过Opt+Freq优化类型,以B3LYP/6-311g基组对10种不同数目及不同位置部分氟代的4-丁基-4’-[(4-丁基苯)乙炔]联苯液晶衍生物分子进行数值计算,根据氟原子的置换位置和数目对这些分子在太赫兹波段的光吸收情况进行了对比分析。结果表明,在太赫兹频段,氟原子置换的位置和数目会显著影响分子内其它官能团的吸收位置和强度。其中苯环内的C-H吸收会因为苯环上氟原子置换数目增加而减少,苯环上双氟原子的增加导致烷烃的吸收峰强度发生变化;对于炔烃,氟原子的置换会通过改变其偶极矩从而产生较强的吸收峰值。计算结果在分子官能团的吸收方面与文献报道的实验测量结果吻合得相当好。根据现有文献报道,作者还对比分析了0.3~3THz范围计算结果与相关文献的实验数据。总之,计算模拟结果能够较好地反应分子材料对太赫兹波的吸收状况,可为相关液晶分子的设计与合成提供参考。

Based on the density functional theory,ten kinds of fluoro-substituted liquid crystal derivative molecules,4-butyl-4’-[(4-butylphenyl)acetylene]biphenyl,are simulated using Gaussian09 package with Opt+Freq optimization type and B3LYP/6-311g basis set.Comparing the substituted position and number of fluorine atoms,the absorption in terahertz region is discussed.The results show that the position and number of fluorine atoms can significantly influence the absorption peak and intensity of the functional groups of the molecule in terahertz region.The absorption of C-H bond of benzene ring will decrease due to increasing numbers of fluorine substitution on the benzene.Two fluorine atoms on the benzene ring will lead to changes in the absorption peak.On the otherhand,the replacement of fluorine atoms of benzene ring can make the alkynes produce a strong absorption peak because of the changing of the molecular dipole moment.The simulation result agrees well with the literature data on the absorption of molecular functional groups.In addition,the calculation result and the experimental data obtained from literatures in 0.3-3 THz range are also analyzed.In conclusion,the simulation result can reflect well the absorption of liquid crystal molecule,which can provide reference for the design and synthesis of related materials.