Phonon, Electronic Structure and Mechanical Properties of Superhard Material BC₂N from First-Principles Calculations

Superhard material BC₂N compound has attracted much attention because of its high hardness and stability. Here, we take Pmm2-BC₂N as an example; the phonon dispersion, electronic structure, and mechanical properties of Pmm2-BC₂N crystal structure are studied theoretically by using first-principles calculation method. The results show that it is dynamically and mechanically stable. The reason of forming strong covalent bonds between B, C, and N atomic orbitals is analyzed by means of state density. The shear modulus, bulk modulus, Young’s modulus, and Poisson’s ratio are calculated. The results show that the shear modulus is larger than that of the bulk modulus, and it is a brittle material. In addition, we calculated the Vickers hardness of Pmm2-BC₂N is 74.9GPa.