First-principles investigation of the structural, electronic and elastic properties of MgxAl4−xSr (x = 0, 0.5, 1) phases

First-principles calculations have been carried out to investigate the structural, electronic and elastic properties of MgxAl4−xSr phases. The calculated lattice parameter c and the cell volume Vcell increase with the increase of Mg content. The calculated formation enthalpies and cohesive energies show that between the two different lattice sites of Al (4d) and Al (4e) in Al4Sr unit cell, the more preferable site of substitution of Mg in Al4Sr lattice is Al (4d) lattice site. And the alloying ability and structural stability of MgxAl4−xSr phases gradually decrease with increasing x. The densities of states (DOS) are obtained to reveal the underlying mechanism of structural stability. The metallicity of the phases is estimated. The bulk modulus, shear modulus, Young's modulus and elastic anisotropy are estimated from the calculated elastic constants. The mechanical properties of these phases are further analyzed and discussed. Gibbs free energy, entropy, Debye temperature and heat capacity are also calculated and discussed.