Ne-HCN体系v_3正则模下红外谱的理论研究

本文采用单双迭代耦合簇理论CCSD(T)方法,采用扩展的相关一致基组aug-cc-p VQZ以及中心键函数(3s3p2d2f1g),对Ne-HCN体系三维势能面和对应于HCN反对称伸缩振动(v_3正则模)下的红外谱进行了理论研究.在保持HCN分子质心不变的情况下,通过将对应不同正则坐标Q_3值的七个二维势能面进行六阶多项式插值可以得到Ne-HCN体系三维势能面.在振动绝热近似下,利用三维势V(Qi3,R,θ)计算得到体系基态v_3=0和第一激发态v_3=1两个振动平均势并用其计算了对应的振动能级.每个绝热势均有两个极小值分别对应于线性(全局极小)和近T型构型(局域极小).基态的全局极小值位于R=8.04 a0,阱深为-60.99 cm-1,第一激发态的全局极小值位于R=8.08 a0,阱深为-59.94 cm-1.在HCN分子v_3模式下,计算得到了104条红外谱线,并对该模式下的红外光谱常数进行预测.

The theoretical study of the infrared spectra for Ne-HCN in the v3 normal-mode vibration of HCN

The potential energy surface (PES) and the infrared spectrum involving anti-symmetric stretching vibration of the monomer HCN molecule are investigated systematically. Calculations have been performed using single and double excitation couple-cluster theory CCSD (T). The augmented correlation-consistent polarized valence quadruple-zeta basis set (aug-cc-PVQZ) with an additional (3s3p2d2f1g) set of bond functions are used to calculate the interaction potential of system. The three-dimensional PES of the Ne-HCN system is achieved by interpolating along Q3 using a six-order polynomial to the seven two-dimensional potential energy surfaces corresponding to the different Q3 coordinates with the fixed center of mass of HCN. Two vibrationally averaged potentials of the complex with HCN molecule at both the ground state(v3=0) and the first vibrational excited states (v3=1 ) are generated based on the three-dimensional PES with the adiabatic approximation. The two vibrational adiabatic surfaces are further used to calculate the bound rovibrational states and the infrared spectrum for the complexes. Each potential is characterized by a global linear minimum and a T-shaped minimum. For the Ne-HCN complex, the global minimum of the ground state locates at R = 8.04 a0 with a depth of -60.99 cm−1, and the global minimum of the first vibrational excited states locates at R = 8.08 a0 with a depth of -59.94 cm−1. The 104 infrared transitions frequencies of Ne-HCN and the molecular constants associated with the v3 normal mode of HCN are predicted.