对称顶原子二聚体的解析莫尔斯/长程模型势及预测的红外和微波光谱：以CH₃F-He为例
Analytical Morse/long-range model potential and predicted infrared and microwave spectra for a symmetric top-atom dimer: a case study of CH₃F-He.
作者信息
Ma Yong-Tao, Zeng Tao, Li Hui
机构信息
Institute of Theoretical Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, 2519 Jiefang Road, Changchun 130023, People's Republic of China.
Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA.
出版信息
J Chem Phys. 2014 Jun 7;140(21):214309. doi: 10.1063/1.4879956.
Four-dimensional ab initio intermolecular potential energy surfaces (PESs) for CH3F-He that explicitly incorporates dependence on the Q3 stretching normal mode of the CH3F molecule and are parametrically dependent on the other averaged intramolecular coordinates have been calculated. Analytical three-dimensional PESs for v3(CH3F) = 0 and 1 are obtained by least-squares fitting the vibrationally averaged potentials to the Morse/Long-Range potential function form. With the 3D PESs, we employ Lanczos algorithm to calculate rovibrational levels of the dimer system. Following some re-assignments, the predicted transition frequencies are in good agreement with experimental microwave data for ortho-CH3F, with the root-mean-square deviation of 0.042 cm(-1). We then provide the first prediction of the infrared and microwave spectra for the para-CH3F-He dimer. The calculated infrared band origin shifts associated with the ν3 fundamental of CH3F are 0.039 and 0.069 cm(-1) for para-CH3F-He and ortho-CH3F-He, respectively.
已计算出CH₃F-He的四维从头算分子间势能面（PESs），该势能面明确包含了对CH₃F分子Q₃伸缩简正模式的依赖性，并且参数化地依赖于其他平均分子内坐标。通过将振动平均势能最小二乘拟合到莫尔斯/长程势函数形式，得到了v₃(CH₃F)=0和1时的解析三维PESs。利用这些三维PESs，我们采用兰索斯算法计算二聚体系统的振转能级。经过一些重新赋值后，预测的跃迁频率与邻-CH₃F的实验微波数据吻合良好，均方根偏差为0.042 cm⁻¹。然后，我们首次预测了对-CH₃F-He二聚体的红外和微波光谱。对于对-CH₃F-He和邻-CH₃F-He，与CH₃F的ν₃基频相关的计算出的红外带起源位移分别为0.039和0.069 cm⁻¹。
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