LiH(D,T)同位素分子从头算的解析势能函数

首先, 利用LiH实验光谱常数和同位素效应推导出LiT分子的光谱学常数. 根据双原子分子的光谱学常数, 力常数, 解析势能函数参数同实验测量的光谱常数间的关系, 推导出LiH和LiD分子的力常数和Murrel-Sorbie解析势能函数参数. 其次, 在核间距平衡点两侧谐振频率范围内取若干点, 用量子化学QCISD(T)方法和6-311++(3df, 2pd)基组对LiH及其氢同位素分子进行单点能计算, 并在Born-Oppenheimer近似下用核动能对电子能量进行修正, 而后进一步拟合为Murrel-Sorbie解析势能函数形式, 得到LiH及其氢同位素分子从头算的解析势能函数参数和力常数. 最后, 对比两种方法推导出的各项参数, 结果说明从头算的修正近似方法是合理的, 可以应用到三原子同位素分子解析势能函数的研究中.

Ab initio analytic potential energy function of of LiH (D,T) isotopic molecules

Firstly, the spectrum constants of LiT molecule were derived from using isotopic effect and the experimental spectrum constants. The results are similar to the spectrum constants of LiT molecule obtained by the corrected approximation theory. After that, we could obtain the force constants of LiH and LiD by using the dependance of spectrum constants on force constants, and used the relationships between the force constants of LiH and LiD and the parameters to derive the parameters of Murrel-Sorbie analytic potential energy functions. Secondly, the single point energy of LiH and its hydrogen isotopic molecules was calculated by quantum method QCISD(T) and basis set 6-311++(3df, 2pd). Then, we corrected the electron energy through nuclear motion energy under the Born-Oppenheimer approximation and fitted Murrel-Sorbie(M-S) analytic potential energy function to the electron energy points. Thirdly, we attained the parameters of ab initio analytic potential energy function and the force constants of LiH and its hydrogen isotopic molecules. As compared to two sets of parameters, it reveals that the ab initio corrected approximate theory method is reasonable and can be applied to a further study of the analytic potential energy function of triatomic isotopic molecules.