First-Principles Investigation of Thermophysical Properties of Cubic ZrC Under High Pressure

Abstract

With a motivation to understand the effect of pressure on the thermophysical properties of a transition metal carbide, zirconium carbide (ZrC) in rock salt (RS) and CsCl phases, a systematic study of the thermodynamic functions with pressure for ZrC in both phases is performed. First-principles theoretical calculations are used, based on density functional perturbation theory within the generalized gradient approximation and with a quasi-harmonic approximation. The results demonstrate that the free and internal energies are greater while the specific heat at constant volume and entropy is smaller for the RS phase of ZrC than for the CsCl phase. The pressure significantly affects the thermodynamic functions. The results also demonstrate that the effect of increasing pressure on ZrC is the same as that of decreasing temperature. The k-point convergence of the phonon spectrum at zero pressure is also analyzed, which may be useful for investigating the pressure-induced dynamic instabilities in the transition metal carbide, ZrC.