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The dynamics of sodium in sodium disilicate: Channel relaxation and sodium diffusion

Juergen Horbach·Walter Kob·Kurt Binder
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Abstract

We use molecular dynamics computer simulations to study the dynamics of amorphous (Na_2O)2(SiO_2). We find that the Na ions move in channels embedded in a SiO_2 matrix. The characteristic distance between these channels gives rise to a prepeak in the structure factor at around q=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, demonstrating that the two processes are closely related.

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Juergen Horbach, Walter Kob, Kurt Binder. 2001-10-16. The dynamics of sodium in sodium disilicate: Channel relaxation and sodium diffusion. https://doi.org/10.1103/physrevlett.88.125502

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