CF_4在外电场作用下分子结构及激发特性研究

Study on Molecular Structure and Excitation Properties of CF_4 under Electric Field

采用密度泛函B3LYP方法在6-311++G基组下优化基态CF4分子,计算出CF4分子键长、偶极距、Mulliken电荷布居分布、分子前线轨道能量和红外光谱等数据,并且在此基础上采用杂化CIS方法计算CF4分子前9个激发态,得到分子激发能、波长和振子强度。研究得出随着电场强度的增加(电场范围在-0.04～0.04a.u.),CF4分子F2—C1键长随着电场强度增加而增大,其余键长减小,分子偶极距先减小后增加,C1电荷布居数先减小后增大,F2电荷布居数线性减小,F3、F4和F5电荷布居数线性增大,分子能隙逐渐减小,在外电场作用下CF4分子结构对称性破坏,红外光谱吸收峰数量增多,吸收峰吸收强度发生不同改变。分子前9个激发态受电场影响明显,激发能随着电场的增加大致呈现先增大后减小的趋势,激发态波长基本为先发生蓝移现象,后呈现红移现象,振子强度变化剧烈,为从光谱方面研究激发态做出理论计算。

The ground-state CF4 molecule was optimized using a density functional theory/B3LYP method in the 6-311+ +G basis set.The bond length,dipole moment,Mulliken charge population distribution,molecular frontier orbital energy and infrared were calculated.Spectral and other data,and based on this hybrid CIS method was used to calculate the first 9 excited states of CF4 molecule,and the molecular excitation energy,wavelength and oscillator strength were obtained.The study shows that as the electric field intensity increases(electric field in the range of-0.04-0.04 a.u.),the F2—C1 bond length of the CF4 molecule increases,and the remaining bond length decreases,and the dipole moment of the molecule decreases first.With the increase,the number of C1 charge population decreases first and then increases.The population of F2 charge population decreases linearly.The population of F3,F4 and F5 charge population increases linearly,and the molecular energy gap decreases.CF4 molecular structure under external electric field Symmetry is destroyed,the number of infrared absorption peaks increases,and the absorption intensity of absorption peaks changes.The first 9 excited states of the molecule are affected by the electric field.The excitation energy increases with the increase of the electric field,and then increases first and then decreases.The excited wavelength is basically aphenomenon of blue shift,followed by a phenomenon of red shift,and intense vibration of the oscillator,to make theoretical calculations for studying excited states from the spectrum.