第一性原理研究Mg2 Si同质异相体的结构、电子结构和弹性性质

在第一性原理框架下,采用赝势平面波方法研究了三种Mg₂Si同质异相体的晶胞结构、电子结构和弹性性质随压强的变化关系.研究发现,反萤石结构Mg₂Si、反氯铅矿结构Mg₂Si和Ni₂In型Mg₂Si分别在压强为0-7 GPa,7.5-20.2 GPa和21.9-40 GPa范围内能够保持结构稳定.计算获得了不同压强下Mg₂Si的弹性常数、体模量、剪切模量、杨氏模量、泊松比和各向异 关键词： 态密度 电子结构 弹性常数 第一性原理

First principles study of structural, electronic and elastic properties of Mg2 Si polymorphs

The structural and the elastic properties of the Mg₂Si polymorphs are calculated. The calculations are performed by using the plane-wave pseudo-potential method within the framework of first principles. The anti-fluorite structure, the anti-cotunnite structure and the Ni₂In-type structure of Mg₂Si can retain their mechanical stability in the pressure intervals 0—7 GPa,7.5—20.2 GPa and 21.9—40 GPa, separately. The relationships between pressure and the elastic moduli (elastic constant, bulk modulus, shear modulus, Young’s modulus, Poisson ratio and anisotropy factor) are discussed. The electron density distribution, the density of states, the bond length and the Mulliken population of these polymorphs are systemically investigated. Our results show that the anti-fluorite Mg₂Si is a semiconductor and the other two polymorphs are metallic materials. The interaction between Mg 2p, 3s and Si 3p plays a dominant role in the stability of the Mg₂Si polymorphs. The strongest interactions in the anti-fluorite Mg₂Si and the Ni₂In-type Mg₂Si are Mg-Mg and Mg-Si interactions, respectively. Our results are concordant with the experimental data and the previous results.