Bonding in B2 and B2+: Insights from full configuration interaction and valence bond studies

Zahid Rashid,Joop H Van Lenthe,Remco W.A Havenith

doi:10.1016/j.comptc.2017.02.001

Abstract

Full Configuration Interaction (Full-CI) and Valence Bond Self-Consistent Field (VBSCF) methods have been used to study the electronic structure and bonding in B2 and B2+ molecules. The bonding analysis based on these calculations shows that the B2 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 B2+ 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.

Highlights

The description of bonding in small molecules remains a challenge: for simple diatomic molecules chemical bonding seems clear, the situation in C2 showed that it can still lead to surprises [1,2,3,4,5,6,7]
We study the nature of the bonding in B2 using full configuration interaction calculations and valence bond calculations, to see if there are similarities in the r bonding situation to
We study the bonding in the ionized B2+ and B22+ species, to elucidate the nature of the chemical bonding with only one or no bonding p electrons

Summary

Introduction

The description of bonding in small molecules remains a challenge: for simple diatomic molecules chemical bonding seems clear, the situation in C2 showed that it can still lead to surprises [1,2,3,4,5,6,7]. Analyses based on full configuration interaction and valence bond calculations [2] and that based on natural orbital functional theory (NOFT) [9] have shown that C2 and its isoelectronic species (CN+, BN and CBÀ) all possess a quadruple bond: a normal r bond, two p bonds and one long, weaker, r bond. Another molecule that may show similar behaviour, as C2, is the B2 molecule. We study the bonding in the ionized B2+ and B22+ species, to elucidate the nature of the chemical bonding with only one or no bonding p electrons

Computational details

Results and discussion

Conclusions