The phase transition and elastic property of osmium carbide under pressure

First-principles calculations of the stabilities, the mechanical properties, and the elastic properties of osmium carbide (OsC) in tungsten carbide (WC) and nickel arsenide (NiAs) structures have been carried out with the plane-wave pseudopotential density functional theory method. WC-OsC is stable in the ground state. The phase-transition pressure from WC structure to NiAs structure is about 7.2 GPa. The pressure dependence of the elastic constants, the aggregate elastic moduli (B, G and E), Poisson's ratio, the Lame constants, the compressibility, and the elastic anisotropy of these two structures are calculated and compared; many differences can be found in the two structures.