First-principles study of phase stability of BN under pressure

The structural and energetic properties of three phases of boron nitride, the graphite-like hexagonal phase (h-BN), the cubic phase (c-BN), and the wurtzite phase (w-BN) have been studied using first-principles pseudopotential calculations. Calculated cohesive energies reveal that c-BN is lower in energy than h-BN by 0.08 eV/atom, in good agreement with the experimental value of 0.17 eV/atom. w-BN is predicted to become a denser phase than c-BN at 16 GPa, in good agreement with experimental observation of a transition from h-BN to w-BN at P>12.5 GPa. The calculated energetic results together with empirical rules on crystal growth provide a good understanding for phase stability and transformation of boron nitride under pressure