Ab Initio, Two-Body and Three-Body Intermolecular Potentials

This chapter examines advances in theory-based intermolecular potentials, particularly ab initio potentials obtained from first principles. Historically, intermolecular potentials have been empirically determined, whereas the advent of recent advances in computational chemistry means that potentials can be determined from first principles or ab initio data. This has resulted in some highly accurate two-body potentials for both atomic systems and some small molecules. Although two-body potentials accurately represent the properties of dilute gases, the prediction of the properties of liquids require the contributions from multi-body interactions. However, the combination of two-body plus three-body interactions is often sufficient to obtain accurate results for the thermodynamic properties of real molecules. Case studies are provided for the prediction of the properties of water using augmented theory-based potentials.