A study was made of the dynamics of the Na atoms in amorphous Na2O–4SiO2 by using classical molecular-dynamics simulations. It was found that the Na trajectories form a well connected network of pockets and pathways intimately related to the location of the non-bridging O atoms. Inside these channels the Na atoms move by activated jumps. By determining the probability that an atom returns to a given starting site, it was shown that at the present concentration of Na, at 1600 to 4000K, such events were not important for the dynamics of this system.

Molecular Dynamics Study of the Diffusion of Sodium in Amorphous Silica. E.Sunyer, P.Jund, W.Kob, R.Jullien: Journal of Non-Crystalline Solids, 2002, 307-310, 939-45