Molekulardynamik-Simulation der Diffusion in binaeren unterkühlten metallischen Schmelzen und Gläsern aus Cu$_{33}$Zr$_{67}$

Kluge, Martin

Book	PreJuSER-34266

Molekulardynamik-Simulation der Diffusion in binaeren unterkühlten metallischen Schmelzen und Gläsern aus Cu$_{33}$Zr$_{67}$

Kluge, M. (Corresponding author)FZJ*

2001
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Berichte des Forschungszentrums 3913, VI, 137 p. (2001)

Please use a persistent id in citations: http://hdl.handle.net/2128/20236

Report No.: Juel-3913

Abstract: The dynamics of atoms in Cu$_{33}$Zr$_{67}$ is studied by molecular dynamics simulations. The time dependent self- and pair-correlations are computed and from these the intermediate self-scattering functions and different structure factors are derived. The diffusion constant is computed from the time development of the self correlation. The deviation of the self correlation function from a Gaussian is quantified. The result reveals heterogenieties in the dynamics of the atoms. The time development of the pair-correlation shows cooperativity in the atomic movement. A simplified model is used for the computation of the isotope effect of diffusion. This leads to an estimate for the number of atoms that move cooperatively. Up to now the shape of the self correlation function was thought to be an indicator for the existence of two different processes contributing to the total diffusion in Cu$_{33}$Zr$_{67}$, but having different temperature dependences. The outcome of the analysis presented in this thesis is, that the diffusion can be traced to one process which is based on atomic jumps. The distributions of jump lengths and jump frequencies are obtained directly from the atomic trajectories. Both are strongly temperature dependent, but there is no change of mechanisms at or near the glass transition temperature. The computations are done over a large temperature interval, covering the melt, the under-cooled melt and the glass. The results of the simulations are compared to different theories about the glass transition (mode coupling theory and trapping diffusion model). Additionally the cooling-rate dependence of the glass transition temperature and the ageing effects are investigated. In summary, this thesis gives a self-contained view of the microscopic processes which lead to diffusion in glasses and melts of Cu$_{33}$Zr$_{67}$.

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