Potential Energy Surface for the H2O-H2 System

In the present paper, we introduce a representation of the potential energy surface for the H2O center dot center dot center dot H-2 system based on orthogonal vectors, assuming that the two molecules are rigid. We represent the interaction potential by an expansion in real hyperspherical harmonics depending on the distance between the centers of mass of the two molecules and oil four angles, which account for two contributions: an external one depending on the three angle variables which define the mutual orientation of the two molecules and an internal one expressed by the angle which describes the position of the oxygen atom in H2O with respect to the H2O center dot center dot center dot H2 system. The surface was generated in the framework of the Supermolecular approach, using the counterpoise-corrected interaction energies at the MP2/aug-cc-pVQZ level. Comparisons with other recent work are presented and features of the representation discussed.