基于密度泛函理论的C_(24)H_(38)O_4分子外场效应研究

各种环境毒物危害着人类的健康,塑化剂更是破坏了食品安全.为研究外电场对塑化剂主要成分之一C_(24)H_(38)O_4(邻苯二甲酸二辛酯,dioctyl phthalate,DOP)的影响,采用密度泛函理论B3LYP方法在6-311G(d,p)基组水平上优化了不同静电场0—0.0125 a.u.(0—6.4278×10~9 V/m)作用下DOP分子的基态几何结构,在此基础上利用同样的方法计算了DOP分子的电偶极矩和分子总能量,最后利用含时密度泛函理论在同一基组下研究了不同外电场对DOP分子紫外-可见(UV-vis)吸收光谱产生的影响,并与实验测得的光谱图进行了比较.结果表明:分子几何构型与电场大小呈现强烈的依赖关系,分子偶极矩随着外电场的增强先减小后增加,而分子总能量随着外电场的增强先增加而后急剧减小;DOP分子激发态的振子强度随着外电场的增强而减小,UV-vis吸收峰显著红移.

Investigation of external electric field effect on C24H38O4 molecule by density functional theory

The C₂₄H₃₈O₄ (dioctyl phthalate, DOP) is a main component of the plasticizer. In order to study the influence of external electrical field on molecular structure and spectrum of DOP, the method B3LYP of the density functional theory at B3LYP/6-311G(d,p) level is employed to calculate geometrical parameters of the ground state of DOP molecule under different external electric fields (from 0 to 0.0125 a.u.) in this article. On this basis, the ultraviolet-visible absorption spectrum of DOP is calculated by using the time-dependent density functional theory in the same fundamental group and compared with the ultraviolet absorption peak of the molecules, measured by UNICO ultraviolet and visible spectrophotometer. Finally, by using the time-dependent density functional theory in the same fundamental group, we study wavelengths and oscillator strengths of the first twenty-six excited states of DOP molecule in external electric field. The obtained results are as follows. The strongest absorption of ultraviolet-visible absorption spectrum appears in the end absorption band from n to σ^* transition. The stronger absorption occurs in the E band of benzene electronic transition from π to π^*. The molecular geometry parameters are strongly dependent on the external field intensity. The dipole moment of DOP molecule is proved to first decrease and then increase with the sharp increase of external field, but the total energy first increases and then decreases with the increase of the external field intensity. The ultraviolet absorption peaks of excited states of DOP are proved to have observably red shift, and the oscillator strength sharply decreases with the increasing of the field intensity.