ABINITIO POTENTIAL-ENERGY SURFACES OF AR-H2O AND AR-D2O

We present an ab initio potential energy surface for the van der Waals system argon-water. The points on the surface are computed as a sum of Heitler-London short range repulsion, damped dispersion, and damped induction. Damping is done in the manner first proposed by Tang and Toennies. We give the surface analytically in the form of a spherical harmonic expansion through l = 7. The expansion coefficients are represented by functions depending on the distance between the centers of mass of the monomers. We also present an Ar-D2O potential obtained from the Ar-H2O potential by translating the center of mass of the water molecule. An analytic formula for the translation of polarizabilities is derived and applied to the computation of the long range energy of Ar-D2O. The short range part of the energy is translated numerically. Finally, the potential is checked by comparison of computed interaction virial coefficients with experimental data.