完全活性空间自洽场方法对NO分子基态势能函数的研究

Study on the potential energy function for the ground state of NO molecule by CASSCF method

利用MOLPRO从头算程序包,选用完全活性空间自洽场(CASSCF)方法并选取cc-pVTZ,cc-pVQZ,cc-pV5Z和cc-pV6Z基组,计算了NO分子基态的平衡核间距与谐振频率,从中优选出cc-pV5Z基组进行单点能扫描,并将扫描结果用最小二乘法拟合得到4参数、5参数、6参数和7参数的MurrellSorbie势能函数.通过比较由势能函数计算出的光谱数据,最终确定6参数的结果最好.最后,利用拟合出的解析势能函数,通过求解径向Schrdinger方程,得到了NO分子基态J=0时的全部38个振动态的振动能级、经典转折点、惯性转动常数以及6个离心畸变常数.

The equilibrium internuclear separation and frequency for the ground-state NO have been calculated by the CASSCF method in the program package MOLPRO in combination with the cc-pVTZ, cc- pVQZ, cc-pVSZ and cc-pV6Z basis sets. The cc-pV5Z basis set is selected as optimal basis to execute a potential energy scanning. The scanning results are fitted to 4-, 5-, 6- and 7-parameter Murrell-Sorbie （M-S） function by the least-squares method. By relative error comparison between the spectroscopic data at present and the experimental data, 6-parameter function is found to be the best one. It shows that the ground-state potential energy curve of NO can be well characterized by the present analytic potential energy function （APEF）. At last, by solving radial Schrodinger equation, the APEF is used to calculate vibration levels, classical turning points, inertial rotation constants and six centrifugal distortion constants of all the 38 vibration states for the ground-state NO molecule when J=0.