Cubic C(3)N: A New Superhard Phase of Carbon-Rich Nitride

Using the particle swarm optimization technique, we proposed a cubic superhard phase of C(3)N (c-C(3)N) with an estimated Vicker’s hardness of 65 GPa, which is more energetically favorable than the recently proposed o-C(3)N. The c-C(3)N is the most stable phase in a pressure range of 6.5–15.4 GPa. Above 15.4 GPa, the most energetic favorable high pressure phase R3m-C(3)N is uncovered. Phonon dispersion and elastic constant calculations confirm the dynamical and mechanical stability of c-C(3)N and R3m-C(3)N at ambient pressure. The electronic structure calculations indicate that both c-C(3)N and R3m-C(3)N are indirect semiconductor.