Novel carbon-rich nitride C3N: A superhard phase in monoclinic symmetry

Abstract

Here, we report the properties of a novel carbon-rich nitride C3N with 3D monoclinic symmetry (m-C3N) from first-principles calculations. The structural, mechanical, elastic anisotropy, and electronic properties of m-C3N were systematically investigated in this work. The m-C3N is a potential superhard material with an estimated hardness of 64.2 GPa. The m-C3N is mechanically and dynamically stable, as confirmed by the elastic constants and phonon spectra. Our results indicate that the m-C3N can be stable up to 100 GPa. Between 0 and 100 GPa, the BH/GH ratio and Poisson’s ratio of m-C3N are less than 1.75 and 0.26, respectively. These ratios reveal that m-C3N exhibits brittle character. Young’s modulus in the (1 0 0) plane of m-C3N has greater anisotropy compared to the (0 0 1) plane, (1 1 1) plane and (0 1 0) plane. Band structure studies show that m-C3N exhibits metal properties at ambient pressure, and it still exhibits metallicity under high pressure (100 GPa).