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摘要: 基于密度泛函理论(DFT)的第一性原理,采用Hartree-Fork(HF)方法,分别计算了SiO2的-石英结构、金红石结构以及氯化钙结构的总能量随体积的变化关系。利用Murnaghan状态方程,通过能量和体积拟合,得到了3种结构的体变模量及其对压强的一阶导数。计算结果表明,随着压强的增加,SiO2会从-石英结构转变为金红石结构,与实验结果和其它理论结果一致;金红石结构与氯化钙结构之间不存在相变,可以共存。此外,对具有-石英结构的SiO2的晶格常数、电子态密度和带隙随压强的变化关系进行了计算和分析,结果表明:加压作用下,能带向高能方向移动,Si─O键缩短,电子数转移增加,带隙展宽,电荷发生重新分布。Abstract: Total energy of SiO2 as a function of unit cell volume has been calculated for -quartz, rutile and CaCl2 structures using the density function theory (DFT) and Hartree-Fork (HF) method. According to the Murnaghan's equation of state, the bulk modulus B0 and B=dB/dp for these three structures have been obtained. The calculated results are all in good agreement with experimental and other theoretical data available in the literature, which indicate that SiO2 will transform from -quartz structure to CaCl2 structure as pressure increasing, and there is no phase transition between rutile structure and CaCl2 structure, namely they can coexist. By analyzing the changes of the lattice parameters, the electronic density of states, and the band gap under pressure, it is found that in -quartz SiO2 the energy band width and charge transfer increase with increasing pressure. Moreover, the Si─O bond length is shortened and the electric charges are redistributed.
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