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Regensburg 2010 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 55: Topical Session Growth Kinetics V

MM 55.5: Talk

Thursday, March 25, 2010, 15:00–15:15, H4

Trapping effects on the critical nucleus size in nucleation a growth processes, kinetic Monte Carlo simulations — •Zoltan Balogh1,2, Zoltan Erdelyi2, and Dezso L Beke21Westfälische Wilhelms Universität-Münster, Institut für Materialphysik, Münster, Germany — 2University of Debrecen, Department of Solid State Physics, Debrecen, Hungary

The critical nucleus size - above which a nucleus will grow and below dissolve - is calculated in a binary alloy during diffusion controlled phase separation using kinetic Monte Carlo simulations. In the calculations the differences in atomic mobilities are often neglected, however the difference of diffusion coefficients in a binary alloys can be as high as 4-8 orders of magnitude in technically important materials (like Si-Ge, Fe-Cr or Ni-Cu).

If the atomic jumps are slower in the A-rich nucleus than in the embedding B-rich matrix, the nucleus will trap the approaching A atoms to its surface. It has not enough time to reject them - despite this process would be favored thermodynamically - before new A atoms arrive. Thus the kinetic and thermodynamical critical size would be different for the nucleus. With reasonable trapping effect the former can be even an order of magnitude smaller than the latter.

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