First-principle calculations on the structural and electronic properties of hard C11N4

A graphite-like C11N4 model was built by stacking graphene and a C3N4 triazine layer and simulated by first principle calculations, which transfers to a diamond-like structure under high pressure. The structural, mechanical, and electronic properties of both materials were calculated. The elastic constants of both materials satisfy the Born-criterion. Furthermore, no imaginary frequencies were observed in phonon calculations. The diamond-like C11N4 is semiconducting and consists of polyhedral and hollow C–N cages. The Vickers hardness of diamond-like C11N4 was calculated to be 58 GPa. The phase transformation from graphite-like to diamond-like C11N4 is proposed to occur at approximately 27.2 GPa based on the pressure-dependent enthalpy.