The outline of my thesis is the following: In Chapter 1, I present more details related to the motivation for studying silica. In Chapter 2, I mainly discuss the force matching method which has been used to construct the force field, and some methology. In Chapter 3, I show how the performance of the potential and how it can be used to calculate infrared and Raman spectra, focusing on the the calcuation of the spectra for high-temperature phase. Based on the calculated specta and the structural analysis, more profound understanding of the silica high-temperature phase is given. I will show in Chapters 4 and 5, pressure–induced changes in oxygen packing in quartz and cristobalite can be understood based on well-known transition paths for close-packing lattices. I will present in Chapter 6, a microscopic picture of the compression mechanisms of silica glass. In order to advance the understanding of pressure-induced amorphization, in Chapter 7 I also studied one example of the silica clathrate (type I) under pressure. I will then summarise the main results of my work in Chapter 8.
