CF_3I分子在外电场中的物理和光谱性质研究

CF_3I是公认的用以代替SF6的新型环保绝缘气体,其在外电场中的具体性质的研究至关重要.利用密度泛函理论(DFT),在B3LYP/DGDZVP基组水平上,从分子结构角度研究了CF_3I气体在外电场(-0. 02 a. u.～0. 02 a. u.)作用下的光谱特征和解离特性.计算结果表明,沿C至I方向的电场增强时:C-I键键长单调增大,能隙E_g单调减小;分子总能量先增大后减小,偶极矩先减小后增大;费米能级EF单调减小,但当电场增至C至I方向0. 010 a. u.时,费米能级EF出现局部极大值.外电场对分子红外光谱的影响表现为:沿C至I方向电场强度增大时,四个振动频率红移(包括最高峰),其余两个蓝移.分子的解离特性表现为:沿C至I方向强度超过0. 025 a. u.的电场可使C-I键断裂.以上结果为CF_3I或其与其混合物在外电场下的特性研究提供了参考.

Study on physical and spectra properties of CF3I under external electrical fields

As a widely regarded environment-friendly alternative of SF6, the studies of the properties of CF3I under the electrical field are of great importance. The density functional theory (DFT) at the B3LYP/ DGDZVP level is employed to find the spectra characteristics and the dissociation properties of CF3I under the external electrical field(-0.02a.u.~ 0.02a.u.). The results indicate that as the external field along the C-I bend direction (from C to I) increases, the length of C-I bond increases and the energy gap of EG decreases, and the total energy of CF3I increases in the beginning and then decreases and the dipole moment behaves contrarily. Meanwhile the Fermi level decreases monotonically but comes to a local maximum value under 0.010a.u. (from C to I). In this process, four frequency of the IR spectra of CF3I redshift (including the peak) and three blue shift. Beside of these, the results show that the external field of 0.025a.u. (from C to I) is sufficient to break the C-I bond. All the above results can provide reference for further research on the properties of CF3I or its mixture gas under external electric fields.