Highly accurate potential energy surface for the He-H-2 dimer
A new highly accurate interaction potential is constructed for the He–H2 van der Waals complex. This potential is fitted to 1900 ab initio energies computed at the very large-basis coupled-cluster level and augmented by corrections for higher-order excitations (up to full configuration interaction level) and the diagonal Born-Oppenheimer correction. At the vibrationally averaged H–H bond length of 1.448736 bohrs, the well depth of our potential, 15.870 ± 0.065 K, is nearly 1 K larger than the most accurate previous studies have indicated. In addition to constructing our own three-dimensional potential in the van der Waals region, we present a reparameterization of the Boothroyd-MartinPeterson potential surface [A. I. Boothroyd, P. G. Martin, and M. R. Peterson, J. Chem. Phys. 119, 3187 (2003)] that is suitable for all configurations of the triatomic system. Finally, we use the newly developed potentials to compute the properties of the lone bound states of 4He–H2 and 3He–H2 and the interaction second virial coefficient of the hydrogen-helium mixture.