Mg-Al-Ca合金中三元Laves相的稳定性和电子结构

Stability and electronic structure of ternary Laves phase in Mg-Al-Ca alloys

采用基于密度泛函理论的第一性原理方法,应用VASP(Vienna Ab-initio Simulation Package)计算软件,研究了Mg-Al-Ca合金中三元Laves相,即Ca(Mg_(1-x),Al_x)_2和Al_2(Ca_(1-x),Mg_x)(x=0,0.25,0.50,0.75,1)在不同形态结构(C14,C15和C36)下的相稳定性及电子结构.计算所得的晶格常数和实验值吻合很好,形成能和相关能的计算用来研究三元Laves相的合金化能力和稳定性,结果表明:C14-Ca(Mg_(0.25),Al_(0.75)_2具有很好的合金化能力,而C15-CaAl_2具有很好的结构稳定性.态密度和电荷密度的计算用来研究Mg-Al-Ca合金中三元Laves相稳定性的内在微观机制.

We have carried out the first--principles theoretical calculations based on density--functional theory to investigate the phase stability and electronic structure of Ca（Mg1-x ,Alx）2 and Al2 （Ca1-x ,Mgx） （x=0, 0.25, 0.50, 0.75, 1） with C14--, C15-- and C36-- structures in Mg-Al-Ca ternary Laves phases. The obtained lattice constants are in good agreement with the experimental values. The heat of formation and cohesive energy are calculated and used to study the stability of Ca（Mg1-x,Alx）2 and Al2 （Ca1-x,Mgx） Laves phases. The results show that C14-Ca（Mg0. 25 ,Al0.75） has the strongest alloying ability and C15-CaAl2 has the best stability of all the investigated Laves phases in Mg-Al-Ca alloy. The density of states （DOS） and charge density distribution are used to study the underlying mechanism of structure and phase stability of ternary Laves phases in Mg-Al-Ca alloys. Key words： first-principles,Mg-Al-Ca alloys, Laves phase, electronic structure