Berlin 2005 – scientific programme

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DY: Dynamik und Statistische Physik

DY 35: Glasses I (joint session DF/DY)

DY 35.7: Talk

Monday, March 7, 2005, 11:45–12:00, TU A060

Structure and transport in amorphous alkali silicates: Computer simulation studies — •Jürgen Horbach, Hans Knoth, and Kurt Binder — Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, D-55099 Mainz, Germany

Mixtures of SiO₂ with an alkali oxide such as Na₂O, Li₂O or K₂O are ion-conducting materials for which the mobility of the alkali ions is much higher than that of silicon and oxygen atoms. We present molecular dynamics simulations for different alkali silicates with an alkali oxide content of about 33 mol%. In combination with inelastic neutron scattering [1] we show in the case of sodium disilicate the existence of a network of diffusion channels for the mobile sodium ions that are reflected by a prepeak in the static structure factor around 0.9 Å⁻¹. In systems with two alkali components (namely Li₂O and K₂O) the mixed alkali effect is seen which is most pronounced at low temperatures where the Si-O matrix is not in equilibrium anymore. We find the formation of two subnetworks of diffusion channels for each alkali component, and we discuss how aging effects in the Si-O matrix affect the diffusion of the alkali ions.

[1] A. Meyer, J. Horbach, W. Kob, F. Kargl, and H. Schober, Phys. Rev. Lett. 93, 027801 (2004).