Abstract: In this paper we report the development of a new approach which can be used to improve supermolecule ab initio intermolecular potentials. It involves combining quantities obtained from low-level dimer calculations (exchange and coulomb energies) with quantities obtained from high-level monomer calculations (charge density overlaps, first-order Coulomb interaction energies and dispersion energy coefficients) in order to estimate the resulting potential energy surfaces at the high level of theory. The level of theory which can be used for both monomer and dimer calculations will increase in time. Therefore, the definitions of ‘low’ and ‘high’ level are flexible and depend on technological limitations: ‘low’ level must be computationally cheap enough to use in thousands of dimer calculations for multidimensional potential energy surfaces, and ‘high’ level is required only in a few monomer calculations. We present results for three homonuclear (He2, Ne2, Ar2) and three heteronuclear (He-Ne, He-Ar, Ne-Ar) rare gas dimers using the MP2 method as the ‘low’ level of theory and the QCISD approach as the ‘high’ level. We compare the extrapolated results with the literature data available for ground state potential energy curves of these dimers.
Keywords: Van der Waals, ab initio, intermolecular potentials, extrapolation
