Atomic geometry and energetics of native defects in cubic boron nitride

We use first-principles calculations to investigate the electronic structur e, atomic geometries and formation energies of point vacancies (V-B, V-N), antisites (B-N, N-B) and interstitials (B-i, N-i) in cubic boron nitride (c -BN). We find that nitrogen and boron vacancies exhibit the lowest formatio n energies in nonstoichiometric c-BN for p-type and n-type conditions, resp ectively, showing intrinsic donor (V-B) and acceptor (V-N) characters. The equilibrium geometries show large outward breathing relaxations for both va cancies and for B-N, With Slight Jahn-Teller distortions from T-d symmetry. For N-B we find an off-center distortion inducing a negative-U behavior in this center. For both interstitial centers we find stable configurations i n which an atomic pair occupies a nitrogen site in the lattice, N-N for Ni and N-B for B-i. These systems are stable for the different charge states i nvestigated.