Mg-Al-Ca-Si合金中二元相的第一性原理研究

First-principles Study on Binary Phase in Mg-Al-Ca-Si Alloy

基于密度泛函理论的第一性原理方法,研究了Mg-Al-Ca-Si合金中主要强化相Al_(2)Ca、Mg_(2)Ca和Mg_(2)Si的晶体结构稳定性、电子性质、弹性常数及声子性质,计算所得的晶格常数、实验数据与文献值吻合。合金形成热和结合能计算结果表明:Al_(2)Ca具有最强的合金形成能力和稳定性。计算了Al_(2)Ca、Mg_(2)Ca和Mg_(2)Si的体模量、剪切模量、杨氏模量和泊松比。结果表明:3种二元相均为脆性相。通过电子态密度、Muliken电子占据数和金属性计算分析结构稳定性机制,表明共价键强弱顺序依次为Al_(2)Ca、Mg_(2)Si、Mg_(2)Ca;声子性质表明Al_(2)Ca、Mg_(2)Ca和Mg_(2)Si分别在5.65、5.93和6.53 THz附近的晶格振动较强。

Based on the first-principles method of density function theory,the crystal structure stability,electronic properties,elastic constants and phono properties of the main strengthening phase Mg_(2)Si,Al_(2)Ca and Mg_(2)Ca in Mg-Al-Ca-Si alloy were studied.The calculated lattice constants are in good agreement with the experimental data and literature values.The calculation results of alloy forming energy and binding energy show that Al_(2)Ca has the strongest alloy forming ability and stability.The bulk modulus,shear modulus,youngs modulus and poissons ratio of Al_(2)Ca,Mg_(2)Ca and Mg_(2)Si were calculated.The results show that the three binary phases are brittle phases;the structural stability mechanism is analyzed by calculation of electron density of states,Mulliken electron occupation number and metallicity.It shows that the order of covalent bond strength is Al_(2)Ca,Mg_(2)Si and Mg_(2)Ca.The phonon properties show that the lattice vibrations of Al_(2)Ca,Mg_(2)Ca and Mg_(2)Si are strong near 5.65,5.93 and 6.53 THz,respectively.