LiB_2和Li_2B分子的结构与势能函数

Structures and analytic potential energy functions of LiB_2 and Li_2B molecules

运用单双取代耦合簇(CCSD)方法,选择基组6-311+g(2df)对基态B2、Li2和LiB分子的微观结构进行优化计算,采用最小二乘法拟合得到B2、Li2和LiB分子的势能函数,并得到了与实验值符合很好的光谱常数.采用同种方法,选择6-311g基组对LiB2、6-31g基组对Li2B分子的基态结构进行优化计算.运用原子分子反应静力学原理得到离解极限.在此基础上,采用多体项展式法,得到LiB2和Li2B分子基态解析势能函数,该势能函数准确再现了LiB2和Li2B分子基态平衡结构特征.

Coupled cluster （CCSD） method has been used to optimize the ground state structures of B2, Al2 and LiB molecules with the 6-311＋g（2df） basis set. The potential energy functions of them have been derived by the least-square fitting method and the calculated spectroscopic constants are in good a- greement with the experimental values. The ground state structures have been optimized by the CCSD/ 6-311g for LiB2, and the CCSD/6-31g for Li2B. Their dissociation limits are induced by employing the principles of atomic and molecular reaction statics. On this basis, the potential energy functions of LiB2 and Li2B have been derived from the many- body expansion theory. The potential energy functions are successfully used for describing the equilibrium geometries of LiB2 and Li2B.