外电场作用下CF_3I分子结构特性及性质

CF_3I由于其良好的绝缘性能和较低的液化温度而作为SF_6替代性气体被广泛研究.本文采用量子化学从头计算法在3-21g基组下优化了CF_3I基态分子结构,得到了基态CF_3I分子的键长、分子前线轨道、Mulliken电荷布居数、红外光谱等.并且在此基础上采用杂化CIS/3-21g方法计算了分子的激发态,得到了分子的激发能、波长和振子强度.结果显示基态CF_3I分子在外电场作用下分子结构发生形变,分子能隙减小,分子活性变强;分子前9个激发态变化明显,随着外电场强度增加,第1、2、9激发能先增大后减小,第3、4、5、6、7与8激发能逐渐减小;第1、2、9激发波长先减小后增大,3、4、5、6、7与8激发波长逐渐增大;在0～0.009 a.u.外电场作用下,第1、2、4、5、6激发态振子强度为零,属于禁阻跃迁,第3、9激发态振子强度随着电场强度的增加而减小,第7、8激发态振子强度随着外电场强度的增加而增加.

Structure and Properties of CF3I Molecule under the Action of External Electric Fields

CF3I has been extensively studied as an alternative SF6 gas due to its good insulating properties and low liquefaction temperature. In this paper, ab initio quantum chemistry calculations were performed to optimize the ground state molecular structure of CF3I under the 3-21g group. The bond length, molecular frontier orbital, ground Milliken population analysis of charge, and infrared spectra of ground state CF3I were obtained. On this basis, the excited state of the molecule was calculated by using the hybrid CIS / 3-21g method. The excitation energy, wavelength and oscillator strength of the molecule were obtained. Results show that under the action of external electric fields the ground state CF3I molecule structure deforms, the molecular energy gap decreases, and the molecular activity becomes stronger. The first 9 excited states of the molecule change obviously. With the increase of the external electric field intensity,1,2,9 excitation can increase and then decrease, the 3, 4, 5, 6, 7 and 8 excitation energy gradually decreased; the 1, 2 and 9 excitation wavelength decreased firstly and then increased, and 3,4,5,6,7 and 8 excitation wavelength increases gradually. Under the external electric fields of 0-0.009au, the 1, 2, 4, 5 and 6 excited oscillator states have zero intensity, which are forbidden transitions. The 3 and 9 excited oscillator strengths decrease with the increase of the external electric field intensity, meanwhile the intensity of the 7 and 8 excited oscillator increases with the increase of the external electric field intensity.