Exploring the structural, phonon dynamical, mechanical and thermodynamic properties of TM2AlC(TM=Ti, Zr and Hf) carbides

Abstract

Although TM2AlC is a promising high-temperature material, the relationship between the mechanical and thermodynamic properties of TM2AlC is unknown. In particular, the structural, mechanical and thermodynamic properties of Hf2AlC carbide are also unknown. To solve these problems, we apply the first-principles method to study the structural, mechanical and thermodynamic properties of TM2AlC phases. Three transition metals (TM = Ti, Zr and Hf) are considered. The calculated result shows that the hexagonal Hf2AlC carbide is firstly predicted based on the formation enthalpy and phonon dispersion. In particular, it is found that the calculated shear modulus, Young's modulus and Vickers hardness of Ti2AlC are higher than that of the Zr2AlC and Hf2AlC. However, the calculated bulk modulus of Hf2AlC is bigger than that of the bulk modulus of Ti2AlC and Zr2AlC. Naturally, the high elastic modulus of TM2AlC carbide is related to the TM-C covalent bond in TM-C layered structure. In addition, it is found that the calculated melting point and Debye temperature of Ti2AlC are bigger than that of the Zr2AlC and Hf2AlC. Therefore, we believe that the Ti2AlC not only has high mechanical properties, but also has excellent thermodynamic properties, which is potentially used in various high-temperature industries.