Ab initio quantum dynamics with very weak van der Waals interactions: Structure and stability of small Li₂(1∑_g ⁺)_n clusters

A computed interaction potential energy surface (PES) for Li₂-He was described. It was obtained at the QCISD(T) level, using quadrupole-zeta basis sets. The rigid rotor part of the PES was employed to generate the total interaction used to describe the forces acting within Li₂-He _n clusters. The realistic quantum mechanical nuclear energies and wave functions were calculated using a DMC approach to the solution of the Schrödinger equation. It was found that the binding energy of the Li ₂ molecule to a ⁴He atom was extremely small.