The computation of intermolecular forces with Gaussian basis functions. Illustration with He2

Abstract

A new and effective technique for basis set augmentation within correlated wavefunction computations of intermolecular forces is illustrated. The technique involves reducing or buffering the ’’ghost orbital’’ basis set borrowing by one species of the functions of a neighboring species when the basis set used to describe each species is not complete. This is achieved by employing a small set of Gaussians (s and higher angular momentum types) moved off the nuclei into the internuclear region. Provided these small sets are carried with each species as the interspecies distance is varied, reliable interspecies potential curves may be obtained. An illustrative application to He2 is described.