Superhard BC_2N: an Orthogonal Crystal Obtained by Transversely Compressing (3,0)-CNTs and (3,0)-BNNTs

By means of density functional theory calculations, an orthogonal boron-carbon-nitrogen compound called (3,0)-BC_2N is predicted, which can be obtained by transversely compressing (3,0) carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs). Its structural stability, elastic properties, mechanical properties and electronic structure are systematically investigated. The results show that (3,0)-BC_2N is a superhard material with a direct bandgap. However, its similar structures, (3,0)-C and (3,0)-BN are indirect semiconductors. Strikingly, (3,0)-C is harder than diamond. We also simulate the x-ray diffraction of (3,0)-BC_2N to support future experimental investigations. In addition, our study shows that the transition from (3,0) CNTS and BNNTs to (3,0)-BC_2N is irreversible.