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本文在从头算CCSD(T)/AVQZ水平上计算了CH_3F-Ar体系包含CH_3F分子Q_3振动的四维势能面.以摩斯长程势(MLR)为模型,分析的三维高精度分子间势能面通过非线性拟合振动平均的基态(v_3=0)和激发态(v_3=1)的能量而得到.其中对2038个格点拟合的方差仅为0.08 cm-1.我们发现,该体系相互作用能的主要贡献来源于短程的交换排斥能和长程的色散能,势能面有3个极小值点,在θ方向表现出强烈的各向异性,而在φ方向各向异性比较弱.与CH_3F-He体系相比,分子间相互作用较强,分子间相互作用对单个分子的束缚较明显,CH_3F和Ar表现得更像紧束缚的超分子.随后,采用径向离散变量表象(DVR)和角度有限基组表象(FBR)相结合的杂化基函数方法进行展开,用Lanzcos迭代的方法计算了该体系的振转能级,并首次报道了该体系的微波、红外光谱.值得指出的是,由于相互作用比较强,形成的势阱较深,该体系在两个不同的势阱中分别形成了分子间振动基态和激发态,这与CH_3F-He体系中全空间离域的能级态形成鲜明的对比.
In this paper, the four-dimensional potential energy surface of CH_3F-Ar system containing Q_3 vibration of CH_3F molecule has been calculated from CCSD (T) / AVQZ ab initio.The Momentum long-range potential (MLR) (V_3 = 0) and the energy of the excited state (v_3 = 1) are linearly fitted to each other, of which the variance of fitting to 2038 grid points is only 0.08 cm-1. We find that the system interaction energy The main contribution comes from short-range exchange repulsion energy and long-range dispersion energy. There are 3 minimum points in the potential energy surface, showing strong anisotropy in θ direction and weak anisotropy in φ direction.Compared with CH_3F- He system, the intermolecular interaction is stronger than that of the He system, and the intermolecular interaction has more binding to a single molecule, and the CH_3F and Ar behave more like the tight binding supermolecules.Secondly, using the radial discrete variable representation (DVR) and the angle (FBR). The Lanzcos iterative method was used to calculate the vibrational energy level of the system, and the microwave and infrared spectra of the system were reported for the first time.It is worth noting that, Due to the strong interaction, the potential well formed is deeper Two different potential wells are formed in the intermolecular vibrations ground and excited states, which CH_3F-He system contrasts the whole space from the domain level states.