High Pressure Effects on Structural, Elastic and Thermodynamic Properties of Tantalum Mononitride

The pressure effects on the structural, elastic and thermodynamic properties of tantalum mononitride in WC-type phase (i.e. WC–TaN) are investigated by the first-principles plane wave pseudo-potential density functional theory method and the quasi-harmonic Debye model. The obtained equilibrium structure parameters and ground state properties are in excellent agreement with the experimental and other theoretical results. The calculations of the phonon dispersion curve and the density of phonon states verify that the WC–TaN is dynamically stable. A full elastic tensor and anisotropies behavior of the WC–TaN is also evaluated and discussed in the wide pressure range. The results show that WC–TaN is elastic anisotropy and mechanically stable up to 100 GPa, and the compression along c-axis direction is more difficult than along a-axis. The obtained superior mechanical properties show that WC–TaN is a promising candidate structure to be one of the ultra-incompressible and hard materials. Finally, by using the quasi-harmonic approximation model, we predicted the thermodynamic properties of WC–TaN under pressure and temperature. The heat capacity CV, Debye temperature θ, the thermal expansion α and the Grüneisen constant γ are obtained successfully in the ranges of 0–100 GPa and 0–2000 K.