Bonding in B 2 and B 2 + : Insights from full configuration interaction and valence bond studies

Full Configuration Interaction (Full-CI) and Valence Bond Self-Consistent Field (VBSCF) methods have been used to study the electronic structure and bonding in B 2 and B 2 + molecules. The bonding analysis based on these calculations shows that the B 2 molecule is stabilised due to the formation of a double σ bond, one strong σ-bond together with one second weaker σ-bond, and two weak π bonds . Upon ionization one π electron is removed from the system and B 2 + is formed, which has a one electron σ bond, instead of a π bond. It has been shown that a few carefully chosen VB configurations are enough to describe the bonding; with these structures, geometrical parameters as well as dissociation energies of these unusual molecular species are in agreement with full-CI results.