Berlin 2008 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 12: Nanostructured Materials IV

MM 12.6: Vortrag

Montag, 25. Februar 2008, 18:00–18:15, H 0107

molecular dynamic simulations of homogeneous nucleation of zinc from the supersaturated vapour phase. — •Frank Römer and Thomas Kraska — Institute for Physical Chemistry, University Cologne, Germany

We investigate the homogeneous nucleation of supersaturated zinc vapour by non-equilibrium molecular dynamics simulation [1]. Argon is added to the vapour phase, which acts as inert gas thermostat to remove the latent heat from the forming clusters. Our simulations cover a temperature range from 400 K to 800 K and a supersaturation ranging from log(S) = 2 to 11. We compare two methods for the detection of clusters namely the Stillinger criterion based on atom distances only and the ten Wolde-Frenkel cluster definition requiring at least five next neighbours for each atom to be part of a cluster. To obtain the nucleation rates and the critical cluster sizes, we use the so-called threshold method by Yasuoka and Matsumoto [2] and a mean first passage time method by Wedekind et al. [3]. The simulation results show large deviation to the classical nucleation theory. A similar deviation has been found for experimental data in comparison with the classical nucleation theory. In conclusion the experimental data and simulations are in different domains with respect to supersaturation but both deviate consistently from the classical nucleation theory.

[1] F. Römer, T. Kraska, J. Chem. Phys. in press;

[2] K. Yasuoka, M. Matsumoto, J. Chem. Phys. 109, 8451 (1998);

[3] J. Wedekind et al., J. Chem. Phys. 126, 134103 (2007)