外电场对对硝基氯苯分子结构与电子光谱影响的研究

为达到降解有机污染物硝基氯苯的目的, 采用外加平行电场的方法, 研究电场对硝基氯苯化合物的分子结构和电子光谱等的影响. 以对硝基氯苯分子为研究对象, 采用密度泛函B3LYP方法在6-311+g(d, p) 基组水平上优化并计算了不同外电场作用下pCNB的基态分子结构、电偶极矩和分子总能量, 在此基础上采用含时密度泛函研究了该分子的前六个激发态的波长、振子强度受外电场的影响规律.结果表明: C–Cl, C–N键长随电场增加而快速增大, 即键能快速减小, 同时苯环上的C–C, C–H键长的变化很小, 且有增有减, 说明分子的降解可能是C–Cl, C–N键断裂而苯环则相对稳定. 同时分子总能量随电场先增大后变小, 电偶极矩刚好相反.另外, 最大吸收波长λ_max 随电场先缓慢减小, 后快速增大, 导致电子跃迁相对容易, 而振子强度随电场变化则相对比较复杂. 关键词： 对硝基氯苯 外电场 密度泛函 含时密度泛函

Influence of external electric field on the molecular structure and electronic spectrum of paranitrochlorobenzene

In order to achieve the goal of degenerating organic pollutant nitrochlorobenzene, the influence of electric field on molecular structure and electronic spectrum and so on is studied by applying an external parallel electric field. Take paranitrochlorobenzene as a study object, the method B3LYP of the density functional theory at 6-311+g(d, p) level is used to calculate its molecucar structure, dipole moments and total energies of the ground state under different external electric fields (from 0 to 0.025 a.u.) in this paper. On this basis, the time-dependent density functional theory is used to study the influences of external electric field on excited wavelength and oscillator strength of the first six excited states. The results show that bond lengths (C–Cl, C–N) increase rapidly and bond energy decrease rapidly with the increase of field intensity. At the same time, bond length (C–C, C–H) changes of benzene ring are very small, and the increases or decreases are not uniform. This illustrates that molecular degradation may lead to the fractures of bonds (C–Cl, C–N), and the benzene ring is relatively stable. what is more, the molecular total energy first increases then decreases, and the dipole moment first decreases then increases with the increase of the field intensity. In addition , the maximum absorption wavelength first slowly decreases, and then increases rapidly with the increase of the field intensity, which causes the electron transition to be relatively easy, while oscillator strength changes relatively complex in anner.
Keywords： paranitrochlorobenzene external electric field denstity functional theory time-dependent density functional theory