Regensburg 2004 – scientific programme

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DF: Dielektrische Festkörper

DF 4: Gl
äser II (gemeinsam FV DF/DY)

DF 4.8: Talk

Tuesday, March 9, 2004, 16:30–16:45, H23

Ion dynamics in single and mixed alkali silicate glasses studied by molecular dynamics simulations — •Heiko Lammert and Andreas Heuer — Westfälische Wilhelms–Universität, Institut für Physikalische Chemie, Corrensstraße 30, D-48149 Münster

We use molecular dynamics (MD) simulations to study the ion dynamics in alkali silicate glasses with the general composition
x  K₂O · (1−x)  Li₂O ·2  SiO₂ , for x=0,0.5,1.

All individual alkali sites provided by the frozen network can be identified by a statistical analysis of MD trajectories, for both the single and the mixed alkali systems. Sites are located by a cluster search on a discretised alkali population density.

The ion dynamics can be analyzed in terms of fast hops between these sites, also yielding average residence times to characterize the sites. As the number of free sites is low compared to the number of ions, correlated back jumps are found to be probable, especially for ions on fast sites. The mobility of ions can be correlated to the local network structure around their site, particularly to the occurence of bridging oxygens.