Scaled perturbation theory for weak intermolecular forces: the helium dimer

Abstract We apply scaled perturbation theory to calculate the potential energy curve of the helium dimer. Particular emphasis is placed on the computationally efficient determination of the exchange–repulsion and dispersion components of the interaction energy, and improving the quality of basis sets which are commonly used to study weak interactions. Our best estimate of the well depth, −11.03 K, is obtained from a potential constructed using no adjustable parameters, and is in excellent agreement with recent benchmark ab initio molecular orbital and quantum Monte Carlo results. Our methodology is suitable for studying much larger systems.