Newly synthesized Zr2AlC, Zr-2(Al0.58Bi0.42)C, Zr-2(Al0.2Sn0.8)C, and Zr-2(Al0.3Sb0.7)C MAX phases: A DFT based first -principles study

作者：Ali M A; Hossain M M; Jahan N; Islam A K M A; Naqib S H

来源：Computational Materials Science, 2017, 131: 139-145.

DOI：10.1016/j.commatsci.2017.01.048

• Bi/Sn/Sb containing MAX compounds
• DFT calculations
• Structural properties
• Elastic constants
• Electronic band structure

The structural, elastic, and electronic properties of newly synthesized Zr-2(Al0.58Bi0.42)C, Zr-2(Al02Sn0.8)C, and Zr-2(Al0.3Sb0.7)C MAX nanolaminates have been studied using first-principles density functional theory (DFT) calculations for the first time. Theoretical Vickers hardness has also been estimated for these compounds. All the calculated results have been compared with experimental data and also with that of recently discovered Zr2AlC phase, where available. Zr-2(AI(0.58)Bi(0),42)C and Zr-2(Al0.2Sn0.8)C are the two first Bi and Sn containing MAX compounds. The optimized structural parameters are found to be in good agreement with the experimental results. The single crystal elastic constants c(ij); and the other polycrystalline elastic coefficients have been calculated and the mechanical stabilities of these compounds have been theoretically confirmed. The bulk modulus increases and the shear modulus decreases due to partial Bi/Sn/Sb substitution for Al in Zr2AlC. The calculated elastic moduli show that these Bi/Sn/Sb containing MAX phases are more anisotropic than Zr2AlC, and have a tendency towards increasing ductility. The Vickers hardness decreases in the Bi/Sn/Sb containing compounds. The charge density mapping reveals mixed chemical bonding characteristics of the nanolaminates under study. Further, the electronic band structures and electronic density of states (EDOS) are calculated and the effects of different elemental substitution on these properties are investigated. The electronic band structures show metallic characteristics with contribution predominantly from the Zr 4d orbitals. Partial presence of Bi/Sn/Sb atoms increases the EDOS at the Fermi level to some extent. Possible implitations of the theoretical results for these recently discovered MAX nanolaminates are discussed in detail in this paper.

• 出版日期2017-4-15