Using density-functional theory calculations, we examine how a mobile single vacancy $\left(V\right)$ interacts with substitutional boron (B) in graphene and the effect of boron-vacancy $\left(\text{B}V\right)$ pairing on the electronic structure of graphene. We find that B in a $\text{B}V$ pair energetically favors fourfold coordination, rather than remaining twofold coordinated, by forming a distorted tetrahedral structure with neighboring C lattice atoms. In the fourfold state, the binding energy of a $\text{B}V$ pair is predicted to be 2.54 eV with respect to B and $V$. Our calculations also suggest magnetic-moment oscillations by interconversion between the twofold $\left(1{\mu }_{\text{B}}\right)$ and fourfold $\left(0{\mu }_{\text{B}}\right)$ states, as their energy difference is rather moderate $\left(\approx 0.3\text{eV}\right)$. We also discuss the bonding mechanisms of a $\text{B}V$ pair in the twofold and fourfold states and modifications in the electronic structure of graphene by $\text{B}V$ pairing as compared to isolated B and $V$ cases. Finally, the pathways and energetics of $V$ migration in the vicinity of B are calculated; the results suggest that B is likely to trap mobile single vacancies within a certain radius and can possibly serve as an anchor for vacancy clusters.

• Received 18 September 2010

DOI:https://doi.org/10.1103/PhysRevB.82.195439