Chunqiang Zhuang

Structural stability, mechanical and electronic properties of cubic BCxN crystals within a random solid solution model

We propose a random solution model for cubic BC(x)N (0.21<x<19.28) crystals and compute the formation energies, elastic moduli and bandgaps for different compositions. Significant deviations of the elastic moduli and lattice parameters from the predictions of Vegards law reveal that the BC(x)N solid solutions are not a simple mixing of diamond and cubic-BN. The computed bandgaps are substantially lower than those of diamond and BN. Compared to BC(2)N, the BC(x)N solids with higher carbon content (x>2) exhibit better structural stability and higher elastic moduli, making them more attractive as potential superhard materials.

Stability and mechanical properties of BCx 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.