Ne-HCN体系v_3正则模下红外谱的理论研究

The theoretical study of the infrared spectra for Ne-HCN in the v_3 normal-mode vibration of HCN

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 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(3 s 3 p 2 d 2 f 1 g)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 Q 3 using a six-order polynomial to the seven two-dimensional potential energy surfaces corresponding to the different Q 3 coordinates with the fixed center of mass of HCN.Two vibrationally averaged potentials of the complex with HCN molecule at both the ground(v 3=0)and the first vibrational excited states(v 3=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 a 0 with a depth of-60.99 cm-1,and the global minimum of the first vibrational excited state locates at R=8.08 a 0 with a depth of-59.94 cm-1.The 104 infrared transitions frequencies of Ne-HCN and the molecular constants associated with the v 3 normal mode of HCN are predicted.