Theoretical calculations for structural, elastic, and thermodynamic properties of c-W3N4 under high pressure

We have investigated the structural and elastic properties of c-W3N4 at high pressures using generalized gradient approximation within the plane-wave pseudopotential density functional theory. The obtained normalized volume dependence of the resulting pressure is in excellent agreement with our experimental data investigated using high-P synchrotron x-ray diffraction. The elastic constants as a function of the applied pressure, the bulk modulus, Young's modulus and shear modulus on the pressure P are also successfully obtained. The superior mechanical properties indicate that c-W3N4 is a potential candidate structure to be one of the ultra-incompressible and hard materials. The high-pressure elastic constants indicate that c-W3N4 is mechanically stable up to 50GPa. By the elastic stability criteria, it is predicted that c-W3N4 is not stable above 110GPa. In addition, the calculated B/G ratio indicated that c-W3N4 possesses ductile nature in the range of pressure from 0 to 50GPa. The calculated elastic anisotropic factors suggest that c-W3N4 is elastically anisotropic. Through the quasi-harmonic Debye model, we also investigate the thermodynamic properties of c-W3N4. (C) 2013 AIP Publishing LLC.