A Novel Superhard Tetragonal Carbon Mononitride

ABSTRACT: We introduced a novel carbon mononitride within tetragonal P42/m symmetry motivated by experimental synthesis and theoretical predictions. Phonon dispersion and formation enthalpy calculations suggest that P42/m-CN is dynamically stable at ambient conditions and can be synthesized at readily attainable pressures. The crystal orientation dependences of the Young’s and shear moduli have been systematically studied for this P42/m phase. Further mechanical calculations suggested that the P42/m-CN is ultracompressible and superhard. The ideal tensile and shear strength at large strains of P42/m-CN are also examined. The results suggest that the weakest tensile strength is along the [100] direction, and the atomic deformation mechanism of P42/m-CN along the weakest shear strength direction (100)[010] is discussed. I