Berlin 2005 – wissenschaftliches Programm

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DY: Dynamik und Statistische Physik

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

DY 35.5: Vortrag

Montag, 7. März 2005, 11:15–11:30, TU A060

Computer Simulations of liquid GeO₂ — •Michael Hawlitzky, Jürgen Horbach, and Kurt Binder — Institut für Physik, Universität Mainz, Staudingerweg 7, D-55128 Mainz

We present molecular dynamics computer simulation results for liquid GeO₂ (at temperatures 6100 K≥ T ≥ 2530K) and compare it with the appropriate results for the homologous substance SiO₂. This has been done by using classical MD (using a model pair potential developed by Oeffner and Elliott) as well as with the Car-Parrinello ab initio technique. We show that the structure and dynamics of GeO₂ exhibit similarities but also distinct differences compared to SiO₂.

In particular, we find that GeO₂ as well as SiO₂ displays a so-called fragile-to-strong transition, i.e. transport coefficients such as the diffusion constants show a change from a power-law behaviour as predicted by mode coupling theory (MCT) at high temperatures to an Arrhenius law at low temperatures. However, in GeO₂ the MCT regime is smaller and the activation energy within the the Arrhenius law regime is, in agreement with experiment, smaller than SiO₂.