Regensburg 2004 – wissenschaftliches Programm
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DF: Dielektrische Festkörper
DF 5: Poster
DF 5.9: Poster
Mittwoch, 10. März 2004, 14:30–18:00, Poster C
Microscopic ion dynamics in lithium silicate glasses studied by molecular dynamics simulations — •Magnus Kunow and Andreas Heuer — Westfälische Wilhelms-Universität, Institut für Physikalische Chemie, and Sonderforschungsbereich 458, Corrensstraße 30, D-48149 Münster
We use molecular dynamics computer simulations to investigate the microscopic ion dynamics in a system consisting of 50 SiO2. Below the computer glass transition temperature the long range alkali dynamics is decoupled from the glass forming species, which provide a quasi-frozen network structure.
To obtain an improved understanding of the alkali dynamics we have varied the conditions of the simulations in two different ways. First, we have artifically immobilized the network. It turns out that the activation energy of the Li diffusion strongly increases. Thus the occurrence of single Li hops strongly depends on local network dynamics. We find that the saddle for a transition between two minimum positions is lowered by the local dynamics of the network. Detailed analysis of trajectories revealed that oxygen atoms near the saddle perform motions opening a No-dqdoorwayNo-dq for the hopping Li ion. Second, we have applied strong electric fields (E ≥ 5*105 V/cm) to our simulations. In this way we obtain information about the current density function of the system in the non-linear response regime which can be directly compared to experimental data from non-linear conductivity measurements. This comparison may help to clarify the information content of this type of experiments.