title: Dynamics of sodium in sodium disilicate: channel relaxation and sodium diffusion.
abstract: We use molecular-dynamics computer simulations to study the dynamics of amorphous (Na2O)2(SiO2). We find that the Na ions move in channels embedded in a SiO2 matrix. The characteristic distance between these channels gives rise to a prepeak in the structure factor at q approximately equal to 0.95 A(-1). The dynamics of sodium is given by a fast process which can be seen in the incoherent scattering function and a slow process which is seen in the coherent function. The relaxation time of the latter coincides with the alpha-relaxation time of the matrix. The Kohlrausch exponent of the fast process for q>1.6 A(-1) is the same as the von Schweidler exponent for the slow one. Thus the two processes are closely related.
authors.affiliation: Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, D-55099 Mainz, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Horbach
authors.forename: Walter
authors.initials: W
authors.lastname: Kob
authors.forename: Kurt
authors.initials: K
authors.lastname: Binder