Ab initio potential energy surface and second virial coefficient for He�H 2O complex

Symmetry-adapted perturbation theory has been applied to compute the helium–water potential with the water molecule assumed rigid. The potential has a single minimum of −34.9 cm−1 at the center of mass separation of 5.92 bohr with the helium atom in the plane of water and making 75° angle with water's symmetry axis (on the oxygen side). The computed points were fitted to an analytic 3D potential surface with correct asymptotic behavior. This potential has been used to calculate the interaction second virial coefficient for He–H2O which agreed well with experimental data and is likely more accurate than the latter.