中文摘要：

采用基于第一性原理的赝势平面波方法系统地计算了Mg2Si基态的电子结构、态密度和光学性质。计算结果表明Mg2Si属于间接带隙半导体，禁带宽度为0．2994eV；其价带主要由Si的3p以及Mg的3s、3p态电子构成，导带主要由Mg的3s、3p以及Si的3p态电子构成；静态介电常数ε1（0）=18．89；折射率n0=4．3460；吸收系数最大峰值为356474．5cm^-1；并利用计算的能带结构和态密度分析了Mg2Si的介电函数、折射率、反射率、吸收系数、光电导率和能量损失函数的计算结果，为Mg2Si的设计与应用提供了理论依据。

英文摘要：

Electronic structure, densities of states and optical properties of Mg2Si have been calculated using the first-principle pseudopotential method. As shown by the calculated results, Mg2Si was predicted to be an indirect semiconductor with the band gap of 0.2994eV; the valence bands of Mg2Si are composed of Si 3p, Mg 3s, 3p and the conduction bands are mainly composed of Mg 3s, 3p as well as Si 3p; ε1（0）=18.89; n0=4.3460; the biggest peak of absorption is 356474.5cm^-1. Furthermore, the dielectric functions, refractivity index, reflectivity, absorption, conductivity and loss function of Mg2Si are analyzed in terms of the calculated band structure and densities of states. The results offer theoretical data for the design and application of Mg2Si.