A DFT insight into the mechanical, electronic and thermodynamic properties of (TiZrHf)C medium-entropy carbide ceramic

Abstract

Recently, a novel medium-entropy transition-metal (TM) carbide (TiZrHf)C has been synthesized with high flexural strength. However, the underlying mechanisms responsible for its outstanding properties are not well understood. Herein, the crystal, mechanical, electronic and thermodynamic properties of (TiZrHf)C are systematically investigated by the first-principles density functional theory (DFT) calculations. The obtained results reveal that the (TiZrHf)C structure is stable in the pressure range of 0 GPa–100 GPa. The elemental random distribution and atomic size difference give rise to local lattice distortion. The lattice distortion, elastic moduli, anisotropy, sound velocity and Debye temperature of (TiZrHf)C increase with the increase of pressure. Electron structure analysis shows that (TiZrHf)C has metallic, ionic and covalent bonding features. The thermodynamic calculation reveals that the thermal expansion and heat capacity of (TiZrHf)C are consistent with that of binary carbides, implying (TiZrHf)C can be used for high temperature applications like traditional carbides.

Keywords

• Medium-entropy carbide ceramics
• Transition-metal carbides
• Elastic constants
• Thermodynamic
• First-principles