First-principles study on the structural, mechanical, electronic, and thermodynamic properties in novel Mg-Li compounds

Magnesium-lithium (Mg-Li) alloys are commonly employed in automotive, aerospace, and biomedicine fields due to their ease of casting, high strength-to-weight ratio, and excellent biocompatibility. A structure screening predicted successfully four unexpected potentially stable Mg-Li compounds (Mg₇Li, Mg₁₁Li₅, Mg₉Li₇, and MgLi₇). The stability calculation results reveal that four compounds are thermodynamically, dynamically, and mechanically stable. Especially, Mg₇Li presents excellent mechanical properties owing to the stronger Li-Li covalent bonds, including bulk modulus with 32.33 GPa, shear modulus with 20.17 GPa, and Young's modulus with 50.09 GPa, which provides a strategy for improving mechanical properties of Mg alloys. Furthermore, the Mg₁₁Li₅ and MgLi₇ exhibit lower lattice thermal conductivity with 0.92 W/mK and 0.71 W/mK, showing that they have potential applications in isolation or insulation materials. The findings are anticipated to yield thorough insight into the intrinsic characteristics in Mg-Li system and provide theoretical data to accelerate the development of high-performance Mg alloys.