Abstract:Mechanical properties and electronic structure of MgCu₂, Mg₂Ca and MgZn₂ phases were investigated by means of first principles calculations from CASTEP program based on density functional theory (DFT). The calculated lattice parameters are in good agreement with the experimental and literature values. The calculated heat of formation and cohesive energies showed that MgCu₂ has the strongest alloying ability and structural stability. Elastic constants of MgCu₂, Mg₂Ca and MgZn₂ were calculated, and the bulk moduli, shear moduli, elastic moduli and Poisson ratio were derived. The calculated results show that MgCu₂, Mg₂Ca and MgZn₂ are all ductile phases. Among the three phases, MgCu₂ has the strongest stiffness and the plasticity of MgZn₂ phase is the best. Melting points of the three phases were predicted using cohesive energy and elastic constants. Density of states (DOS), Mulliken population, electron occupation number and charge density difference were discussed. Finally, Debye temperature was calculated and discussed.

Key words: magnesium alloy; MgCu₂; Mg₂Ca; MgZn₂; Laves phases; electronic structure; mechanical property; Debye temperature