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The mechanical properties of L12 type Al3X (X = Mg, Sc, Zr) have been investigated by first‐principles calculations. The calculated elastic properties showed that Al3Sc was the stiffest and intrinsically brittle, while Al3Mg was the softest and exhibited ductility tendency. The obtained stress–strain curves demonstrated that both of the ideal tensile and shear strengths of Al3Zr were the strongest, followed by Al3Sc and Al3Mg, and Al3Zr was also the most ductile among three phases, which disagreed with the prediction from the calculated elastic properties, indicating that the mechanical properties should be measured from the complete stress–strain relations at both small and large strains. The electronic density of states (DOS) especially the variations of the charge density during the strain loading were investigated to unveil the intrinsic mechanism for the mechanical properties of L12 type Al3X (X = Mg, Sc, Zr) phases.

First-principles calculations have been carried out to investigate the elastic properties and electronic structures of the main binary Mg-Ce phases MgCe, Mg 2 Ce, and Mg 3 Ce. The optimized equilibrium lattice constants are in agreement with the available experimental values, and the structural stability of MgCe, Mg 2 Ce, and Mg 3 Ce is studied from the calculated heat of formation and cohesive energy. The elastic constants C ij of these phases are calculated; then the bulk modulus, shear modulus, Young's modulus, Cauchy pressure, and the ratio of bulk to shear modulus B/G are further investigated. The obtained results indicate that Mg 2 Ce has the best ductility and plasticity, while Mg 3 Ce is the hardest and the most brittle among the three Mg-Ce phases. The density of states (DOSs) and charge density distribution of the Mg-Ce phases are also calculated to reveal the underlying mechanism for the structural stability and elastic properties of these Mg-Ce phases.