First-principles calculations, into the stability, tensile strength, and physical properties of M2CuC (M = V, Cr, and Mo) as novel 211 MAX phase carbides

Abstract

The stability and properties of newly proposed 211 MAX phase carbides, M₂CuC (M = V, Cr, and Mo), were investigated using first-principles calculations. We assessed their thermodynamic, dynamical, and mechanical stability via formation energies, phonon dispersion analyses, and elastic constants. Electronic band structures and density of states confirm their metallic nature. We visualized their anisotropic mechanical properties—Young's modulus (E), linear compressibility (β), and shear modulus (G) within the x–z plane—using 2D and 3D representations.

Vickers hardness calculations revealed differences in ductility. Tensile strength analysis reveals directional dependence, with V₂CuC showing the highest values in both [0 0 1] (13.23 GPa, 7 %) and [110] (13.82 GPa, 20 %) directions. Cr₂CuC exhibits greater ductility in [001], while Mo₂CuC consistently shows the lowest tensile performance. Using Slack's model, we estimated room-temperature lattice thermal conductivities as 21, 19.5, and 16.7 W/m·K for Cr₂CuC, V₂CuC, and Mo₂CuC, respectively. We also explored additional thermal parameters (including Debye and melting temperatures) to evaluate their suitability for extreme environments.