中文摘要：

α-石英、β-石英、α-方石英、β-方石英和超石英是自然界中SiO2常见的五种晶型．本文利用第一性原理平面波赝势方法，系统计算了五种SiO2晶体的体弹性模量、电荷密度、电子态密度，能带结构，并和可获得的实验进行了比较．α-石英、β-石英和具有空间群Fd3m结构的β方石英显示间接的带隙，而α-方石英，超石英和具有空间群P2，3和142d结构的β-方石英显示直接的带隙．五种晶型SiO2的带隙宽度均大于5．5eV，都是绝缘体．

英文摘要：

In nature there are five different types of SiO2 crystals （α-quart, β-quar, α-cristobalite, β-cristohalite and stishovite）. In this paper the atomic and electronic structures of these SiO2 crystals are investigated from the plane wave pseudopotential method, and compared with the available experimental data. α-quart, β-quar and β-cristobalite with the space-group Fd3m symmetry exhibit the indirect band gap, whereas the band gaps of α-cristobalite, stishovite, β-cristobalite with P213 and I42d are direct. The band gap values of all types of SiO2 crystals are more than 5.5eV, indicating that they are all insulators.