A comparative study the structural, mechanical, and electronic properties of medium-entropy MAX phase (TiZrHf)2SC with Ti2SC, Zr2SC, Hf2SC via first-principles

Abstract

MAX phases refer to a class of transition metal carbides or nitrides with a layered hexagonal structure, with a general chemical formula Mn+1AXn, where M denotes transition group metal elements, A denotes the 13th and 14th group elements, and X denotes carbon (C) or nitrogen (N) element. MAX phases can be used as a precursor for two-dimensional (2D) MXenes. The MAX phase can be used as a precursor for preparing two-dimensional (2D) layered MXenes. MXenes are a research frontier for electrochemical energy storage materials. Recently, a new kind of multicomponent MAX phases has been synthesized and attracted considerable research attention. However, the physical and material properties of multicomponent MAX phases are still poorly understood. Herein, the structural, mechanical, and electronic properties of a recently synthesized (TiZrHf)2SC multicomponent MAX phase are systematically investigated by density functional theory (DFT) calculations in comparison with the traditional Ti2SC, Zr2SC, Hf2SC phases. The obtained results reveal that (TiZrHf)2SC exhibits good crystal stability, intrinsic brittleness, mechanical anisotropy, and severe local lattice distortion. Lattice distortion would alter charge distribution and chemical bonds, therefore influence the mechanical and electrical properties. The sound velocity and Debye temperature of (TiZrHf)2SC are higher than Hf2SC, but lower than Ti2SC and Zr2SC. Electronic analysis reveals that (TiZrHf)2SC has both metallic conductivity and covalent features.

Keywords

• Multicomponent MAX phases
• Elastic constants
• Anisotropy
• Structural stability
• First-principles