Basis set extension effects on the He2 interaction energy components

Electrostatic, exchange, classical induction, and charge‐transfer components of the He2 interaction energy have been analyzed within our previously proposed SCF interaction energy decomposition scheme [36] employing full counterpoise correction of the basis set superposition error (BSSE). The results have been supplemented by dispersion energies evaluated within the variation‐perturbation approach. The basis sets used here have been systematically increased in order to investigate basis set extension effects and perform a thorough test of our decomposition scheme. The results obtained for He2 at its van der Waals minimum (R = 5.6 a.u.) indicate that interaction energy components corrected by the full counterpoise method display reduced basis set dependency, do not seem to be overcorrected by the Jansen–Ros–Boys–Bernardi approach, and converge toward the most accurate values available in the literature. The correct representation of occupied orbitals in He requires the use of at least 1s primitive is Gaussian orbitals. This explains the inconclusive character of previous attempts to resolve the BSSE overcorrection problem within smaller expansions.