A theoretical study of the structure, bonding, and vibrational frequency shifts of the H₂-HF complex

The complex formed from hydrogen fluoride and the hydrogen molecule has been investigated theoretically in two ways. Large basis, well-correlated ab initio electronic structure calculations have been used to map out regions of the potential energy surface and an electrical interaction model has been used to find the classical intermolecular interaction effects. From the ab initio potential surface, the fundamental vibrational transition frequencies of hydrogen and hydrogen fluoride are predicted to be red shifted by 20 and 15 cm^-1, respectively. The Liu and Dykstra theory of vibrational frequency shifts that uses the intermolecular electrical interaction yields shifts of 31 and 19 cm^-1, respectively. The equilibrium structure of the molecule is T shaped, a feature that is determined by electrical interaction, and the well depth is around 300 cm^-1. A significant fraction of the well-depth results from electron correlation effects.