Study of dynamics and structure in sodium silicate glasses. Molecular dynamics simulation.

We conduct molecular dynamics simulations to study dynamics and structure of sodium silicate glasses through Voronoi polyhedron and diffusion path consisting of Ox-polyhedrons connected via XY-lines. The result shows that Six-polyhedrons and the number of Ox-polyhedrons do not contain Na. Most of NBFx-polyhedrons contain 1, 2 or not Na, where BO, NBF is the O bonded with 2 and 1 or not Si, respectively. Average volume per polyhedron increases in order: Six-polyhedron → BOx-polyhedron → NBFx-polyhedron. Na atoms are concentrated in NBFx-polyhedrons and frequently move through them leading to very fast diffusivity of Na in comparison with Si and O. The simulation shows that the number of neighbors around NBFx-polyhedron is larger than that around BOx-polyhedron. Major Na atoms move over BN- and NN-lines connecting with NBFx-polyhedrons. Moreover, Na atoms displace through the preferential diffusion path comprising mainly of NBFx-polyhedrons. The correlation effect is significant for sodium diffusion.