Stability and mechanical properties of BC(x) crystals: the role of B-B bonds and boron concentration.

Based on a random solid solution model, first-principles calculations were performed to investigate the structural stabilities and mechanical properties of cubic BC(x) (1 < x < 63) crystals. Judging by the formation energy, hardness and ductility, a boron concentration between 2.8 × 10(21) and 8.4 × 10(21) cm(-3) (1.56-4.69 at.%) is a compromise choice to balance the structural stabilities and mechanical properties of BC(x) crystals. The ratio of B-B bonds has an evident effect on the structural stability of the cubic BC(x) crystals. Controlling the ratio of B-B bonds in the precursor materials might be a practicable route for synthesizing BC(x) crystals with higher boron concentrations.