First-principle investigation of the structural, electronic, elastic, and elastic anisotropy properties and thermal stabilities of CeMg₂Si₂ and Mg₂Si

Based on the density functional theory (DFT), first-principle calculation methods were employed to calculate and systematically investigate the structural, electronic, elastic, and elastic anisotropy properties of CeMg₂Si₂ and Mg₂Si phases, which were recently found to coexist. A calculation of the cohesive energies and formation enthalpies show that Mg₂Si has higher structural stability than CeMg₂Si₂, and it is easier to form CeMg₂Si₂ than Mg₂Si under the same conditions. An analysis of the electronic structures indicates that various bonds, including typical metallic, ionic, and covalent bonds, exist simultaneously in the CeMg₂Si₂ phase. An analysis of the elastic properties show that both phases are mechanically stable and that the CeMg₂Si₂ phase exhibits higher hardness than the Mg₂Si phase. Calculation results of the mechanical modulus show that CeMg₂Si₂ achieves a better performance than Mg₂Si regarding stiffness, resistance to volume changes, and plastic deformations. In addition, CeMg₂Si₂ and Mg₂Si is evidently brittle; evaluations indicate that Mg₂Si exhibits elastic isotropy, whereas CeMg₂Si₂ shows elastic anisotropy. A Debye temperature prediction indicates that Mg₂Si achieves better thermal stability than CeMg₂Si₂. The current investigation provides a comprehensive understanding of the strengthening mechanism of different intermetallic phases in Si-containing magnesium alloys and helps optimize various characteristics, such as hardness, ductility, and heat-resistance of magnesium alloy, by forming extensive tiny intermetallic phases during solidification. (paper)