Van der Waals interaction between linear molecules

Abstract

First a standard expansion in spherical harmonics for the interaction of elongated axial-symmetric molecules obeying the law r−2n is derived, where an integral representation for the coefficients is given. In the second step we will show how the integrals can be evaluated and present the coefficients as analytical functions of the distance between two molecules and their dimensions as well. This is carried out explicitly in the case of the London–van der Waals interaction (r−6) for linear centrosymmetric molecules up to the fourth order term.