Long-range coefficients for molecular interactions

Abstract

General formulae for the coefficients C n shaping the long-range behaviour of electrostatic, induction and dispersion interactions between molecular systems, are given in terms of the spherical tensor theory in its real form. The coefficients depend on a function P, describing in a compact way the relative orientation of the partners, and the permanent and induced moments of the individual molecules. Use of a hypergeneralized London formula allows the molecular dispersion coefficients to be expressed in terms of static multipole polarizabilities and their related excitation energies. Explicit formulae are presented for the first few coefficients of the linear water dimer (H 2O 2) 2. The transformation properties of the real spherical tensors under rotation and translation of the origin of the body-fixed reference frame are given in appendices, together with tables containing the coefficients needed in the expansion of the electric potential due to a non-uniform external field as well as the explicit relations connecting real spherical and cartesian forms for molecular moments and polarizabilities up to l = 3.