  The structural, elastic, and electronic properties of newly synthesized
Zr2(Al0.58Bi0.42)C, Zr2(Al0.2Sn0.8)C, and Zr2(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 are compared with
experimental data and also with that of recently discovered Zr2AlC phase, where
available. Zr2(Al0.58Bi0.42)C and Zr2(Al0.2Sn0.8)C are the two first Bi and Sn
containing MAX compounds. The calculated structural parameters are found to be
in good agreement with the experimental data. The single crystal elastic
constants Cij and 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 ductility. The Vickers
hardness decreases in the Bi/Sn/Sb containing compounds. 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 coming from the Zr 4d orbitals.
Partial presence of Bi/Sn/Sb atoms increases the EDOS at the Fermi level to
some extent. Possible implications of the theoretical results for these
recently discovered MAX nanolaminates have been discussed in detail in this
paper.
