In order to determine the origin of the diffusion channels observed in sodium silicate glasses, classical molecular dynamics simulations of Na2O–4SiO2 were performed, during which the mass of the Si and O atoms was multiplied by a tuning coefficient. It was observed that the channels disappeared and that the diffusive motion of the Na atoms vanished if this coefficient was greater than a threshold value. Above this threshold, the vibrational states of the matrix were not compatible with those of the Na ions. The decrease in diffusion was attributed to the absence of resonance conditions.

Matrix-Controlled Channel Diffusion of Sodium in Amorphous Silica. E.Sunyer, P.Jund, R.Jullien: Journal of Physics - Condensed Matter, 2003, 15[26], L431-7