UCLA

This dissertation contributes to decode the relationship between glass composition and various properties that are crucial to novel glass design by performing molecular dynamics simulations. The topics include the prediction of glass transition temperature, the origin of glass-forming ability, and the impact of cooling rate on glass relaxation. In general, the first two properties are analyzed by utilizing topological constraint theory. By combining molecular dynamics simulations and topological constraint theory, a fully analytical model is developed to predict the fictive glass transition temperature of (CaO)x(SiO2)1-x glass system. To be specific, this model takes composition as input and provides the prediction of glass transition temperature as output. On the other hand, glass-forming ability is an important factor that guides the manufacturing process while sometimes imposes limitations to glass engineering. Despite many empirical successes to identify and characterize glass-forming ability in various glass systems, there exists a lack of knowledge of physical details in the glass structure. Here, we conduct molecular dynamics simulations of a series of calcium silicate glasses. We show that the flexible-to-rigid topological transition coincides with the compositional window that has optimal glass-forming ability. By explaining this transition from the aspect of internal flexibility and internal stress within the network, we aim to provide an alternative topological explanation for the nature of glass-forming ability. Chapter 3 is a reprint of a previously published journal article. It demonstrates the impact of cooling rate on glass transition by analyzing glass relaxation and hysteresis of a series of silicate glasses. It proves that by extrapolating simulation data, one can access the results that are close to those generated from experimental cooling rates.