First-principles calculations for the mechanical properties of BC5

We employ ab initio plane-wave pseudo potential density functional theory to calculate the equilibrium lattice parameters, elastic constants, anisotropies, Poisson's ratios, and the Cauchy violation under hydrostatic pressures of 0-60 GPa for BC5 with hexagonal P3m1 and tetragonal I4m2 structures. The results show that two structures are stable under high pressure and the incompressibility increases with pressure. In addition, the electron structures, the total and the partial densities of states are also calculated. BC5 is found to be metallic with band gap, unlike other B-C compounds. The material properties of BC5 are mainly determined by B 2p(1) and C 2p(2) electronic states together. All these show that BC5 is an unusual super hard material, and it may be a potential candidate for diamond at high temperature. The given density of states indicates the covalent hybridization between B and C atoms in this compound. The pressure slightly influences the density of states and the band gap, indicating stability under high pressure. We also find that pressure has no influence on the density of states near Fermi level and the band gap, except for slight shifts of the bands. It can be further inferred that BC5 will have good stability under high pressure.