Reliable isotropic and anisotropic dipolar dispersion energies, evaluated using constrained dipole oscillator strength techniques, with application to interactions involving H2, N2, and the rare gases

Abstract

Molecular dipole oscillator strength distributions (DOSDS), which are reliable in the sense of yielding accurate results for the various dipole properties of molecules, can be constructed if sufficient input information is available. The DOSDS are constructed from extensive experimental and theoretical information, including oscillator strength and photoabsorption cross section data, and are constrained to reproduce accurate refractivity measurements of the relevant dilute gases and to satisfy oscillator strength sum rules. The techniques for obtaining the DOSDS, and related properties, are well established for the evaluation of reliable isotropic dipolar dispersion energies. In this paper they are extended to the evaluation of anisotropic dipole properties, with particular emphasis on anisotropic dispersion energies. The approach used will be illustrated with applications involving H2, N2, and the rare gases. Also included will be brief discussions on (i) the use of reliable results for the dipole–dipole and triple–dipole dispersion energies in constructing complete two- and many-body potential energies and (ii) the advantages of constrained DOSD methods, relative to other approaches, for determining all the dipole properties of molecules.