Structure, stability and defects of single layer hexagonal BN in comparison to graphene.

We study by molecular dynamics the structural properties of single layer hexagonal boron nitride (h-BN) in comparison to graphene. We show that the Tersoff bond order potential developed for BN by Albe et al (1997 Radiat. Eff. Defects Solids 141 85-97) gives a thermally stable hexagonal single layer with a bending constant κ = 0.54 eV at T = 0. We find that the non-monotonic behaviour of the lattice parameter, the expansion of the interatomic distance and the growth of the bending rigidity with temperature are qualitatively similar to those of graphene. Conversely, the energetics of point defects is extremely different: instead of Stone-Wales defects, the two lowest energy defects in h-BN involve either a broken bond or an out-of-plane displacement of a N atom to form a tetrahedron with three B atoms in the plane. We provide the formation energies and an estimate of the energy barriers.