外电场作用下SF6分子结构与红外光谱

采用密度泛函LSDA方法，在6-311++g(3df,3pd)基组水平上研究了不同外电场下SF6分子的几何结构、偶极矩、能级分布和红外光谱的变化规律，并利用杂化CIS方法研究了SF6分子的前9个激发态的激发能、波长和振子强度随外电场的变化情况。结果表明：X轴向上的1S-6F键长受到外场影响最大，随着外电场的增加可能最先趋于断裂；偶极矩随外场的增加而增大，分子总能量随外场的增加而减小；LUMO能级较HOMO能级受外电场影响大，能隙随外场增大而减小；红外光谱吸收峰随外场增大而分开，同时部分原本不具有红外活性的振动模式变成了具有一定的红外活性；激发波长、振子强度、激发能也受外电场影响，但随电场变化比较复杂。

The Molecular Structure and Infrared Spectrum for SF6 under External Electric Fields

The LSDA method of density functional theory at 6-311++g(3df, 3pd) level is used to study the geometrical parameters, dipole moments, energy levels and infrared spectra of the ground state of SF6 molecule under different external electric fields in this paper. On the basis of this, the single-excitation configuration interaction (CIS) is used to study the influences of external electric field on the excited energies, excited wavelengths and oscillators of the first nine excited states. The results show that the bond lengths (1S-6F) will be greatest impact by X axial electric field, and with the continue increase of electric field, it may be the first to break. The total energy gradually decreases, but the dipole moment increases with increase of the external field. The LUMO energy levels are greatly influenced by external electric fields, but the HOMO energy levels are less affected by the external electric fields. The absorption peak of infrared spectrum is separated when the external electric field is increased, and part of the vibration mode without infrared activity becomes to have some infrared activity. The excited energies, excited wavelengths and oscillators are influenced by electric fields, but their changes with the electric field are relatively complex.