Extrapolation methods and scaled perturbation theory for determining intermolecular potential energy surfaces

We construct potential energy curves for six rare-gas dimers and several 1-D cuts through two H-2 ... rare-gas potential energy surfaces using two methods. The first is based on supermolecule dimer calculations at a low level of theory, extrapolated using monomer calculations at higher levels of theory. The second is based on perturbation theory calculations, where the effects of intramolecular electron correlation on different interaction terms are treated using approximate scaling relationships. Both methods are competitive with supermolecule dimer calculations at higher levels of theory and provide computationally efficient means of studying weakly bound systems. The methods are therefore suitable for calculations on larger systems for which accurate supermolecule methods would be computationally expensive. (C) 2003 Wiley Periodicals, Inc.