Prediction of a Low-Dense BC₂N Phase

We predict a low-dense phase of ternary boron-carbon-nitrogen compound with a cubic symmetry, named as ld−BC₂N. Crystal and electronic structures are studied by the ab initio pseudopotential density functional method. Lattice constant, electronic band structure and density of state as well as the phonon spectrum of ld−BC₂N are calculated. Our results show that ld−BC₂N is an indirect gap semiconductor with a band gap of 3.6 eV, a theoretical Vickers hardness of 67.5 GPa and the bulk modulus of 280 GPa suggest that ld−BC₂N is a superhard material which has low elastic moduli and high hardness compared with cubic BN.