An “electrons-in-molecule’' model for atom–atom representation of atom–molecule potentials, with application to the Ar–B2(X3Σg-) complex

Abstract

A flexible model for generating the anisotropic atom–atom form of an atom–diatom potential is developed and used to fit the high-level abinitio PES (potential energy surface) of the ground state Ar–B₂ Van der Waals complex. The system is found to have only a well for the T-shaped geometry as a consequence of the sp-hybridisation of B within B₂. Comparison of the complex with similar Ar–X₂ species studied at the same level of theory exhibits some particular features of the boron system, originating from its electronic structure and interpreted in terms of the Ar–B interactions. A proper combination of the empirically adjusted potentials for isolated ArB and of the calculated effective atom–atom potentials acting in Ar–B₂ is employed to produce the “real’' PES of the complex, used to predict its microwave spectrum.