The shape type of bonds and the direction of phonons in orthorhombic BC₂N from first-principles calculations

BC₂N (space group p222₁) is a super hard material, which can be regarded as the replacement of atoms from diamond-structure (FD3M). It is necessary to clarify the microstructure due to that the hybrid bond and electronic orbit can reveal the fertile micro-theory of diamond-like materials. In this way, the first-principles calculated electronic properties and phonons are presented in this paper. The optimized structure shows that there are four hybrid orbits in BC₂N crystal because of the different shapes of the electron clouds. Then, the acoustic phonons show that the BC₂N has a big mechanical modulus. And, the bonds between element N and C as well as B and C are more active than the others two bonds due to the low frequency and the low intensity of phonon.