First-principles study on mechanical properties of LaMg₃ and LaCuMg₂

Abstract

With the substitution of part Mg in LaMg₃ by Cu, the elastic constants C₁₁ and C₁₂ increase while C₄₄ decreases, implying an enhanced Poisson effect and smaller resistance to 〈001〉(100) shear. Furthermore, the bulk modulus B increases, while the shear modulus G, elastic modulus E and anisotropic ratio A are reduced. The calculated Debye temperature of LaCuMg₂ is lower, implying the weaker interaction between atoms in LaCuMg₂. Then, the stress-strain curves in entire range and the ideal strength at critical strain are studied. The present results show that the lowest ideal tensile strength for LaMg₃ and LaCuMg₂ is in the 〈100〉 direction. The ideal shear strength on the

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slip system of LaMg₃ is greater than LaCuMg₂. The density of states and charge density distribution are further studied to understand the inherent mechanism of the mechanical properties.

Keywords

first-principle calculations / elastic constant / ideal strength / mechanical properties / electronic structure

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