微扰理论将一个具有分子间相互作用的位能E。（r”,/）的实际系统看作是位能为Ez”厂N,/）的参考系统的微扰系,即E;‘’一E。一氏”,E;1’为位能的微扰项。实际系统的自由能等其它性质,可围绕参考系统相应性质展开为Taylor级数,微扰展开项只涉及Ez“和参考系统的分布函数 Perturbation theory will be a potential for intermolecular interactions E. (R “, /) is considered as the perturbation system of the reference system of Eq. One of the perturbation terms for the potential energy is E ’1’. The other properties of the real system such as the free energy can be expanded to the Taylor series based on the corresponding properties of the reference system. The perturbation expansion terms only concern the distribution of Ez ”and the reference system function