Design of basis sets for precise intermolecular force computation. Investigation of the He2 potential curve using CEPA-PNO correlated wavefunctions.

Abstract

Techniques for the systematic improvement of atomic (or molecular) basis sets for precise intermolecular force computations are used to refine the theoretical He2 ground state potential curve. Diagnostic parameters from the most recent experimental study of this curve (re=5.61a0, De=10.57 °K) are matched in the present work (re=5.63a0, De=10.55 °K). Specifications for the minimum basis capable of yielding a reliable He2 potential curve are elucidated, opening the way for a definitive determination of this curve from first principles.