Molecular dynamics computer simulations were used to study the dynamics of amorphous (Na2O)•2(SiO2). It was found that the Na ions move in channels embedded in a SiO2 matrix. The characteristic distance between these channels gave rise to a pre-peak in the structure factor at a q value of about 0.95/Å. The dynamics of Na was given by a fast process which could be seen in the incoherent scattering function and a slow process which was seen in the coherent function. The relaxation time of the latter coincides with the α-relaxation time of the matrix. The Kohlrausch exponent of the fast process for q > 1.6/Å was the same as the von Schweidler exponent for the slow one. Thus the two processes were closely related.

Dynamics of Sodium in Sodium Disilicate - Channel Relaxation and Sodium Diffusion. J.Horbach, W.Kob, K.Binder: Physical Review Letters, 2002, 88[12], 125502 (4pp)