石英α-SiO₂晶体基本特性的原子模拟

Atomic Simulation of Basic Properties for α-SiO₂ Crystal

摘要: 采用分子动力学的方法，结合tersoff势函数，研究了石英α-SiO₂晶体融化过程以及在外载条件下完整晶体和微裂纹晶体的基本力学性能。通过体积温度曲线可以得到α-SiO₂晶体随着温度的升高体积出现了前期的急剧膨胀和后期的缓慢增加，直到趋于稳定的变化，说明在升温过程中α-SiO₂晶体出现了结构的变化。同时研究了α-SiO₂在常温单轴加载下的力学性能，研究结果表明α-SiO₂晶体在加载过程中经历弹性变形、塑性变形以及断裂变形三个阶段，其中获得的完整晶体的屈服强度为22.6 GPa，断裂强度为36 GPa，说明α-SiO₂晶体具有很好的强度。而微裂纹晶体的屈服强度为20.7 GPa，断裂强度为20 GPa，表明α-SiO₂晶体断裂方式为脆性断裂。

Abstract: The melting process and the basic mechanical properties of perfect crystal and microcrack models for α-SiO₂ crystal are studied with tersoff potential function under external loading by molecular dynamics simulation. The volume-temperature curve shows that the volume of the α-SiO₂ crystal shows a sharp expansion in the early stage and a slow increase in the later stage with the increasing of temperature, until it reaches a stable change, which indicates that the structure of the α-SiO₂ crystal changes during the heating process. At the same time, the mechanical properties of α-SiO₂ under uniaxial loading at room temperature are studied. The results show that the α-SiO₂ crystal experiences three stages of elastic deformation, plastic deformation and fracture deformation during the loading process. The yield strength of the perfect crystal is 22.6 GPa, and the fracture strength is 36 GPa, indicating that the α-SiO₂ has good strength. But the yield strength and fracture strength of the microcrack model of α-SiO₂ are 20.7 GPa and 20 GPa, respectively, which show that the fracture mode of the α-SiO₂ crystal presents brittle fracture.