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.

超硬材料BC ₂ N化合物因其高硬度和稳定性而备受关注。这里我们以Pmm2-BC ₂ N为例；采用第一性原理计算方法，从理论上研究了Pmm2-BC ₂ N晶体结构的声子色散、电子结构和力学性能。结果表明，它是动态和机械稳定的。B、C、N原子轨道之间形成强共价键的原因是通过状态密度分析的。计算剪切模量、体积模量、杨氏模量和泊松比。结果表明，剪切模量大于体积模量，为脆性材料。此外，我们计算了 Pmm2-BC 的维氏硬度₂ N 为 74.9GPa。