Link between structural and mechanical stability of fcc- and bcc-based ordered Mg-Li alloys

The first principles pseudopotential calculations based on the Perdew-Burke-Ernzerhof (PBE) form of generalized gradient approximation (GGA) within density functional theory (DFT) have been utilized to investigate the structural and elastic properties of cubic-based Mg-Li alloys. The heats of formation and elastic moduli were used in predicting structural stability profile, and their results are consistent with each other. In terms of phase stability, an interesting correlation between the calculated tetragonal shear modulus (C′) and formation energy of corresponding bcc and fcc ordered compounds relative to hcp Mg and Li lattices is drawn. The predicted stability trend due to structural energy difference was further confirmed by electronic structure calculations based on Jones-type analysis.