Ab initiostudies of the (111) and ( 1¯ 1¯ 1¯) surfaces of cubic BN: Structure and energetics

We present ab initio local-density-functional investigations of the (111) and (111) surfaces of cubic BN. We give a detailed geometrical analysis of different reconstructions, namely, the (1×{}1), the (2×{}1), and several (2×{}2) patterns. We compare the stability of models with different stoichiometries as a function of the chemical potential. Stable phases as a function of nitrogen chemical potential are predicted for both surfaces. In a B-rich environment the N-adatom and in a N-rich environment the nitrogen-triangle patterns are realized on the (111) surface. We predict two phase transitions on the (111) surface: as the N chemical potential increases, the boron-triangle, the (2×{}1), and the nitrogen-triangle reconstructions are realized.