First-principles study of O-BN: A <i>sp</i>3-bonding boron nitride allotrope

Abstract

A fully tetrahedrally bonded boron nitride (BN) allotrope with an orthorhombic structure (O-BN) was investigated through first-principles calculations. O-BN has a bulk modulus of 371.8 GPa and a hardness of 66.4 GPa, thereby making it a superhard material with potential technological and industrial applications. O-BN becomes thermodynamically more stable than layered hexagonal BN (h-BN) at pressure above 1.5 GPa and is more favorable than the recently reported Pct-BN at any pressure. The phase transformations from h-BN and BN nanotubes to O-BN were respectively simulated, indicating the feasible synthesis of this superhard phase.