Using monomer properties to obtain integrated intensities for vibrational transitions of van der Waals complexes

Abstract

The integrated intensities of vibrational transitions depend on the magnitude of the derivatives of the dipole with respect to nuclear motion. Normally, the only reliable way to compute such derivatives is by tedious and expensive ab initio calculations. In this paper, we present a simplification for weakly bound complexes based on distributed schemes for describing the charge densities and polarizabilities of the monomers. Formulations based on both Cartesian and spherical harmonics are presented. The results for both these schemes agree exactly with each other, and qualitatively with full ab initio calculations for the hydrogen fluoride dimer, (HF)₂.