Physical properties of hexagonal WN2 under pressure

A first-principles study on the mechanical stability, elastic and thermodynamic properties of WN2 with P63/mmc and P-6m2 phases are reported using the pseudo potential plane wave method within the generalized gradient approx- imation. The calculated equilibrium parameters are in good agreement with the available theoretical data. A complete elastic tensor and crystal anisotropies of the ultra-incompressible WN2 are determined in the wide pressure range. By the elastic stability criteria, it is predicted that P63/mmc and P-6m2 phases in WN2 are not stable above 175.1 GPa and 170.1 GPa, respectively. Finally, by using the quasiharmonic Debye model, the isothermal and adiabatic bulk modulus, and the heat capacity of WN2 are also successfully obtained.