A New Potential Superhard Phase of $OsN_2$

A new phase of C2/m $OsN_2$ is proposed in this paper. The crystal structure, elasticity and electronic properties of C2/m $OsN_2$ were studied by first-principles calculations. The elastic constants, the elastic moduli (B, G, and E) and Poisson's ratio v of $OsN_2$ have been investigated. From the first-principles calculations, we find that C2/m $OsN_2$ is metallic and mechanically stable. The quasi-harmonic Debye model, using a set of total energy versus molar volume obtained from the first-principles calculations, is applied to the study of the thermal and vibrational effects. The dependence of structural parameters, thermal expansions, heat capacities, Grüneisen parameters and Debye temperatures on the temperature and pressure are obtained in the whole pressure range from 0 to 80 GPa and temperature range from 0 to 800 K as well as compared with available data.