Interactions of Hydrogen Molecules with Halogen-Containing Diatomics from Ab Initio Calculations: Spherical-Harmonics Representation and Characterization of the Intermolecular Potentials

TL;DR

This study uses ab initio calculations to analyze the potential energy surfaces of hydrogen molecule interactions with halogen-containing diatomics, employing spherical-harmonics representation to characterize isotropic and anisotropic contributions.

Contribution

It introduces a spherical-harmonics approach to represent and analyze PESs for H2 interactions with halogen diatomics, linking parameters to molecular properties for interaction insights.

Findings

Spherical-harmonics representation effectively models PESs.

Comparison with Pirani et al.'s potential function shows good agreement.

Analysis reveals the nature of isotropic and anisotropic interaction contributions.

Abstract

For the prototypical diatomic-molecule - diatomic molecule interactions H2-HX and H2-X2, where X = F, Cl, Br, quantum-chemical ab initio calculations are carried out on grids of the configuration space, which permit a spherical-harmonics representation of the potential energy surfaces (PESs). Dimer geometries are considered for sets of representative leading configurations, and the PESs are analyzed in terms of isotropic and anisotropic contributions. The leading configurations are individuated by selecting a minimal set of mutual orientations of molecules needed to build the spherical-harmonic expansion on geometrical and symmetry grounds. The terms of the PESs corresponding to repulsive and bonding dimer geometries and the averaged isotropic term, for each pair of interacting molecules, are compared with representations in terms of a potential function proposed by Pirani et al. (see Chem. Phys. Lett. 2004, 394, 37-44 and references therein). Connections of the involved parameters with molecular properties provide insight into the nature of the interactions.