First-Principle Calculations of the MgYA_4(A=Co and Ni)Phase with AuBe_5-Type Structure

摘要

First-principles calculations have been performed to study the structural,mechanical and magnetic properties of the MgYCo_4 and MgYNi_4 phases in AuBe_5-type structure.The obtained values of cohesive energy as well as formation energy prove that the MgYCo_4 and MgYNi_4 phases have a good combination of structural stability and alloying ability,which is also supported by electronic structure.It is found that the magnetic moment of the MgYCo_4 phase is 19.06 μ_B per unit cell mainly owed to the 3d state of Co atom,and the MgYNi_4 phase exhibits no magnetism.Both the trigonal shear constant C_(44) and the shear modulus G of the Mg YNi_4 phase are larger than those of the MgYCo_4 phase.Plasticity of alloys has been estimated by the C_(11)-C_(12) and Young's modulus E,and C_(12)-C_(44),shear to bulk modulus ratio G/B and Poisson's ratio v have been studied to predict the ductility of alloys.According to the calculated results,the MgYCo_4 phase has better plasticity as well as ductility,compared with the MgYNi_4 phase.