First-principles study of the structural, electronic, elastic, and high-pressure properties of the (V2/3Zr1/3)2AlC i-MAX phase and M2AlC (M = V, Zr) MAX phases

Abstract

Structural materials are crucial in energy and power generation, transportation, infrastructure, and space exploration. A thorough understanding of their mechanical and high pressure behavior is critical to tuning their properties for extreme environment applications. We employed density functional theory to investigate the structural, electronic, and mechanical properties, as well as high pressure behavior of a Zr-based i-MAX phase, (V_2/3Zr_1/3)₂AlC, alongside its precursor MAX phases, M₂AlC (M = V, Zr). These systems show a metallic nature due to the significant contribution of the d-orbitals of the transition elements (M = V, Zr). We quantitatively analyze their chemical bonding using the quantum theory of atoms in molecules and crystals (QTAIMAC). We explore a strong correlation between their mechanical properties and chemical bonding. The enhanced elastic properties of V₂AlC are due to its robust chemical bonding and high covalence. The (V_2/3Zr_1/3)₂AlC exhibits significant anisotropy, comparable mechanical properties, and marginal brittleness. The bulk modulus of all these materials is greater than the shear modulus, suggesting that shear constrains their stability. The aluminum (Al) atoms govern the high pressure behavior of these systems. Our work underscores the significance of tailoring chemical bonding through crystal structure and chemistry to optimize the intrinsic mechanical properties of (V_2/3Zr_1/3)₂AlC and M₂AlC (M = V, Zr) for advanced nuclear energy systems.