An overlap expansion method for improving ab initio model potentials:Anistropic intermolecular potentials of N_2,CO,and C_2H_2 with He~*(2~3S)

摘要

An overlap expansion method is proposed for improving ab initio model potentials.Correction terms are expanded in terms of overlap integrals between orbitals of the interacting system.The method is used to improve ab initio model potentails for N_2+He~* (2 ~3 S),CO+He~*(2 ~3S),and C_2H_2+He~*(2 ~3S).Physical meanings of the optimization are elucidated in terms of target orbitals.Correction terms are found to be dominated by the components of HOMO,LUMO,next-HOMO,and next-LUMO on the target molecule.The present overlap expansion method using a limited number of correction terms related to frontier orbitals provides an efficient and intuitive approach for construction of highly anistropic intermolecular interaction potentials.