GLASS-TRANSITION TEMPERATURES STUDIED BY MD SIMULATION OF SOME ALKALIMETASILICATES

Molecular dynamics simulation of some alkali metasilicates (M2SiO3, M = Li, Na, K) was performed to compare glass transition temperatures, T (g), defined in various ways. The potential parameters derived from ab initio MO calculations were used and found to reproduce the inflectio n of V-T relation on cooling the system. The T(g) defined by the infle ction point corresponds well to that defined by geometrical changes of coordination polyhedra found in previous work. The self-diffusion coe fficients of the alkali ions in higher temperature regions were shown to be related to the amount of free volume in these systems.