AN ACCURATE AB-INITIO POTENTIAL-ENERGY SURFACE OF HE-H2O

We present an accurate calculation of the intermolecular potential sur face for the van der Waals complex He-H2O using complete fourth-order Moller-Plesset perturbation theory (MP4) with an efficient basis set c ontaining bond functions. The calculation gives a global minimum at R = 3.15 Angstrom, theta = 105 degrees, phi = 0 degrees (in a Jacobi coo rdinate system) with a minimum energy D-e = -31.8 cm(-1), along with b arriers of 13.4 and 12.6 cm(-1) for in-plane rotation at theta = 0 deg rees and 180 degrees, respectively, and a barrier of 20.0 cm(-1) for o ut-of-plane rotation at theta = 105 degrees, phi = 90 degrees. The pot ential energy surface is compared with previously published surfaces f or He-H2O, and with the potential energy surface for Ar-H2O.