Mg-Zn-Y-La合金中二元相的电子结构,力学性质和光学性质的第一性原理计算

First-principles calculation of electronic structure, Mechanical properties and optical properties of binary phases in Mg-Zn-Y-La alloy

摘要:

为了研究稀土元素对镁锌合金性能的影响,利用基于第一性原理计算的平面波赝势方法,对Mg₂Y、Mg₂La和Mg₃La的结构稳定性、电子结构、力学和光学性能进行了计算和分析。形成热和结合能的计算结果表明,Mg₃La具有最强合金化能力,而Mg₂La具有最强的结构稳定性。通过电子态密度(DOS),电子占据数和差分电荷密度分析了结构的稳定机制。计算了三种结构的弹性常数,并进一步得到了体模量B,剪切模量G,杨氏模量E和泊松比ν等。计算结果表明：Mg₂Y具有最强的抵抗变形能力,Mg₃La具有最强的刚度和抵抗剪切变形能力,而Mg₂La塑性最强。进一步分析表明Mg₂Y和Mg₂La为延性相,而Mg₃La为脆性相。此外,硬度和熔点的计算结果表明,三种金属间化合物中,Mg₃La的耐磨性最好,Mg₂Y的耐热性最好。最后计算并分析了三种晶体结构的折射率,反射率,吸收系数和损失函数。

Abstract:

In order to investigate the effect of rare earth elements on the properties of Mg-Zn magnesium alloys, the structural stability, electronic structure, elastic and optical properties of Mg₂Y, Mg₂La and Mg₃La are calculated and analyzed by using the plane wave pseudo-potential method based on the first principles calculation. The calculated heats of formation and cohesive energies show that Mg₃La has the strongest forming ability and Mg₂La has the most stable structure. The stabilization mechanism of the structure is analyzed based on the calculation of electron densities of states (DOS), electron occupation number and electron density difference. The bulk modulus B, shear modulus G, Young"s modulus E, and Poisson"s ratio ν are further calculated by the elastic constants. The calculated results show that Mg₂Y has the strongest ability of resisting deformation, Mg₃La has the strongest stiffness and resistance to shear deformation, Mg₂La has the strongest plasticity, Mg₂Y and Mg₂La are ductile phases while Mg₃La is brittle phase. Furthermore, the calculated results of hardness and melting temperature shown that Mg₃La has the best abrasive resistance and Mg₂Y has the best heat resistance among the three intermetallic compounds. Finally, the refractive index, reflectivity, absorption coefficient and loss function of the three crystal structures were calculated and analyzed..