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采用基于密度泛函理论的第一性原理赝势平面波方法,计算了Mg-Al-Si-Ca合金系金属间化合物Mg2Si,Mg2Ca,Al2Ca以及Si2Ca四相的形成焓,结合能,弹性常数及态密度。形成焓和结合能的计算结果表明:Al2Ca的合金化能力最强,Si2Ca相的结构最稳定;体模量(B)、剪切模量(G)、杨氏模量(E)和泊松比(ν)的计算结果表明:四相均为脆性相,且Mg2Si相的塑性最差,结合弹性模量和态密度分析,得出Mg2Ca的塑性最好;态密度和Mulliken布居分析表明:四相中均存在离子键和共价键,共价键由强到弱顺序为Si2Ca,Al2Ca,Mg2Si,Mg2Ca;而离子键强弱顺序按Mg2Si,Al2Ca,Si2Ca,Mg2Ca依次递减;而Si2Ca最稳定的原因是其共价键比其他三相更强。
The formation enthalpies, bonding energies, elastic constants and states of the Mg2Si, Mg2Ca, Al2Ca and Si2Ca phases in Mg-Al-Si-Ca alloy system were calculated using the first-principles pseudopotential plane wave method based on density functional theory density. The formation enthalpies and binding energies show that Al2Ca has the strongest alloying ability and the most stable structure of Si2Ca phase. The bulk modulus (B), shear modulus (G), Young’s modulus (E) and Poisson’s ratio (ν) results show that: all four phases are brittle phase, and Mg2Si phase plasticity of the worst, combined with the elastic modulus and density of state analysis, the plasticity of Mg2Ca obtained the best; state density and Mulliken population analysis showed that: four In the phase, ionic and covalent bonds exist, and the order of the covalent bonds from strong to weak is Si2Ca, Al2Ca, Mg2Si and Mg2Ca; and the order of the ionic bond decreases in order of Mg2Si, Al2Ca, Si2Ca and Mg2Ca, while the most stable Si2Ca The reason is that its covalent bond is stronger than the other three phases.