First-principles investigation of the binary AB_2 type Laves phase in Mg-Al-Ca alloy: Electronic structure and elastic properties

摘要

First-principles calculations have been carried out to investigate the electronic structure and mechanical properties of the main binary Laves phase CaMg_2, CaAl_2 and MgAl_2 with C14, C15 and C36 structures in Mg-Al-Ca alloy, respectively. The optimized structural parameters were in very good agreement with the experimental values. The calculated heat of formation and cohesive energy showed that the C15-CaAl_2 Laves phase was of the strongest alloying ability and structural stability. The electronic density of states (DOS) and charge density distribution were given. The elastic parameters C_(ij) were calculated, then the bulk modulus, shear modulus, Young's modulus, Possion's ratio and anisotropy value were derived. The ductility and plasticity were discussed in comparison with the previous experimental and theoretical data. The results showed that C14-MgAl_2 is of the best ductility and C15-MgAl2 is of the best plasticity in the investigated binary alloys.