Abinitio study of boron, nitrogen, and boron–nitrogen clusters. I. Isomers and thermochemistry of B3, B2N, BN2, and N3

TLDR: In this article, the relative stability of the isomers was determined using full fourth-order Mo/ller-Plesset theory, both with and without spin projection, as well as coupled cluster methods.

Abstract: For a number of different structures and states of B3, B2N, BN2, and N3, optimum geometries and harmonic spectra were obtained at the HF/6‐31G* level. The relative stability of the isomers was determined using full fourth‐order Mo/ller–Plesset theory, both with and without spin projection, as well as coupled cluster methods. Estimates for the dissociation energies are based on scaled CCD+ST(CCD) binding energies. Koopmans’ vertical ionization potentials and Mulliken charge distributions, both at the UHF/6‐31G* level, are quoted for the most stable isomers. B3 is found to be an equilateral triangle in its 2A’1 ground state. B2N has a symmetric linear arrangement in its 2Σ+u ground state with an extremely low bending frequency (73 cm−1), and an unusually low vertical ionization potential (6.75 eV). Its asymmetric stretching (2021 cm−1) is found to be extremely intense (8782 km mol−1). BN2 has four rather closely spaced states, of which an isosceles triangle is the absolute minimum (2A1 state). However, at h...