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多氯联苯(PCBs)是难降解有机污染物,2,2′,5,5′-四氯联苯(PCB52)是PCBs的一种,研究通过对PCB52分子加外电场的方法来降解该物质.采用密度泛函B3LYP方法在6-311+g(d)基组水平上优化并计算了不同外电场(0.04—0.04 a.u.)作用下PCB52的基态分子结构参数、分子总能量、电偶极矩和电荷分布.然后利用含时密度泛函方法研究了PCB52分子在外电场下的前六个激发态的波长、激发能量和振子强度的影响.结果表明:随着外电场的增加,1C21Cl和14C 20Cl键的键长增大;PCB52的两个苯环在外加电场下,二面角增大,分子毒性减弱;PCB52分子能隙减小,导致分子更容易受激发而跃迁到激发态发生还原脱氯反应.外电场的增大,激发态的激发能在迅速减小,吸收波长也迅速红移,振子强度不再为零.表明电场作用下,分子易于激发和解离.
Polychlorinated biphenyls (PCBs) are refractory organic pollutants. 2,2 ’, 5,5’-tetrachlorobiphenyl (PCB52) is a kind of PCBs. The degradation of the PCB52 molecule by an external electric field The density functional B3LYP method was used to optimize and calculate the ground state molecular structural parameters, total molecular energies, electric dipoles of PCB52 under the different external electric field (0.04-0.04 au) at the level of 6-311 + g (d) Moment and charge distribution. The influence of the wavelength, excitation energy and oscillator strength on the first six excited states of PCB52 molecules under external electric field was studied by using time-dependent density functional theory. The results show that with the increase of external electric field, 20Cl bond length increases; PCB52 two benzene rings in the applied electric field, the dihedral angle increases, the molecular toxicity weakened; PCB52 molecular gap decreases, leading to more easily excited by the molecules and transition to excited state restore off Chlorine reaction.The increase of the external electric field, the excitation energy of the excited state is rapidly reduced, the absorption wavelength is rapidly redshifted, and the strength of the vibrator is no longer zero, indicating that the molecule is easy to be excited and dissociated under the action of an electric field.