Pressure and temperature effects on (TiZrTa)C medium-entropy carbide from first-principles

Abstract

Multicomponent carbides have recently received considerable interest because of their remarkable material properties and vast material composition space compared to traditional carbides. However, the underlying physical mechanisms of multicomponent carbides remain poorly understood, particularly involving high pressure and temperature applications. Herein, the impacts of pressure and temperature on the stability, mechanical, and thermophysical properties of (TiZrTa)C are explored and evaluated by the density functional theory (DFT) computations. The study demonstrates that (TiZrTa)C is mechanically and thermally stable even at 100 GPa or 1500 K. (TiZrTa)C exhibits significant local lattice distortion, metallic conductivity, mechanical anisotropy, and covalent characteristics. Lattice distortion stems from the covalent bond length and angle variation caused by the random distribution of metal elements. Elevated pressure increases the elastic constants, Young's modulus, Bulk modulus, shear modulus, hardness, and fracture toughness of (TiZrTa)C. Increasing temperature leads to decrease the elastic constants and mechanical stiffness of (TiZrTa)C. The hybridization of C-p electrons and M-d electrons results in forming a pseudogap near the Fermi level and directional covalent bonds within the crystal. (TiZrTa)C has similar material properties to binary carbides, meaning that it has the potential to be used as a viable ultra-high temperature ceramic.