Berlin 2005 – wissenschaftliches Programm

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M: Metallphysik

M 12: Flüssige und amorphe Metalle III

M 12.3: Vortrag

Freitag, 4. März 2005, 15:15–15:30, TU H111

Structure and Dynamics of Amorphous Al-Ni Mixtures: Computer Simulations — •Subir K. Das, Jürgen Horbach, and Kurt Binder — Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, D-55099 Mainz, Germany

A Monte Carlo (MC) and Molecular Dynamics (MD) computer simulation techniques are used to study the structure and dynamics of amorphous Al-Ni mixtures. The simulations are done at constant pressure (p=0) to allow a direct comparison with experiments. As a model an embedded atom potential [1] is used. We elucidate the appearance of the prepeak in the experimental neutron scattering structure factor in Al-rich compositions [2]. Diffusion constants are computed as a function of composition and temperature. They show a good agreement with neutron scattering experiments [3] for different compositions and also for Al₈₀Ni₂₀ at different temperatures above 1000K (below that temperature crystallites are formed in the experiment whereas in the simulation the system can be supercooled). We study the dynamics of supercooled Al₈₀Ni₂₀ and analyze its properties by means of mode coupling theory. In particular, we show how the intermediate range order, as reflected by the aforementioned prepeak, affects the dynamics. Moreover, the validity of the Stokes-Einstein relation is checked.

[1] Mishin et al., Phys. Rev. B 65, 224114 (2002). [2] Maret et al., Phys. Rev. B 42, 1598 (1990). [3] S. K. Das, J. Horbach, M. M. Koza, S. Mavila Chatoth, A. Meyer, submitted to Appl. Phys. Lett.