Molecular-dynamics study of glass formation in the Li₂SiO₃ system

Abstract

A molecular-dynamics simulation is carried out to study the changes in statistical geometry and related dynamical properties in the Li₂SiO₃ system at the glass transition point. The number of oxygens around each cation within the first coordination shell is taken as the number V of vertices of the polyhedron that characterizes the system. When the number N of O-O pairs that are shorter than R _O (R _O is the position where the second plateau of the running coordination number n _O-O(r) ends) is counted, the distribution of N is found to have a maximum at N = 3V - 6 (V = 3, …, 7) below the glass transition temperature. N corresponds to the number of contact pairs in each polyhedron. The lifetime of the polyhedron with N = 3V - 6 is found to be longer than other polyhedra with other values of N. The results suggest that geometrical degrees of freedom play an important role in glass formation in this system.