First principle study on the mechanical response of ZrC and ZrN at high-pressure conditions: anisotropy perspective

ABSTRACT

We perform full-potential density functional theory calculations to study the mechanical properties of ZrC and ZrN ceramics in the pressure range of 0-100 GPa. Birch-Murnaghan (B-M) isothermal equation of state was used to estimate energy-volume relationship and related structural parameters. We use Viogt-Reuss-Hill (VRH) approximation to account for the polycrystalline elasticity of the compounds. We calculate elastic constants as a function of pressure and cover bulk, shear, and Young’s moduli, hardness, and Poisson’s ratio. For each property, we report the yields of Voigt, Reuss, and Hill approximations as a function of pressure. The pressure-dependent absolute and universal anisotropy have also been reported. We follow our calculations by exploring the brittleness/ductility of ZrN and ZrC by calculating Cauchy pressure and Pugh’s ratio. Among thermal properties, we calculate minimum thermal conductivity and Debye temperature. The calculated results indicate that ZrN has higher bulk modulus; however, the shear and Young’s modulus are comparable for ZrC and ZrN at all pressures. ZrN has a higher Poisson ratio but, ZrC shows higher hardness in the calculated pressure range. Excluding Poisson’s ratio, pressure has an increasing effect on these properties, where the rate of increase is almost identical for both compounds.

KEYWORDS:

• ZrC and ZrN
• DFT
• high pressure
• Voigt–Reuss–Hill
• anisotropy

Acknowledgment

The support from Shahid Beheshti University is gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the author(s).