Diffusion and interdiffusion in binary metallic melts

P. Kuhn, J. Horbach, F. Kargl, A. Meyer, and Th. Voigtmann
Phys. Rev. B 90, 024309 – Published 29 July 2014

Abstract

We discuss the dependence of self- and interdiffusion coefficients on temperature and composition for two prototypical binary metallic melts, Al-Ni and Zr-Ni, in molecular-dynamics computer simulations and the mode-coupling theory of the glass transition (MCT). Dynamical processes that are mainly entropic in origin slow down mass transport (as expressed through self-diffusion) in the mixture as compared to the ideal-mixing contribution. Interdiffusion of chemical species is a competition of slow kinetic modes with a strong thermodynamic driving force that is caused by nonentropic interactions. The combination of both dynamic and thermodynamic effects causes qualitative differences in the concentration dependence of self-diffusion and interdiffusion coefficients. At high temperatures, the thermodynamic enhancement of interdiffusion prevails, while at low temperatures, kinetic effects dominate the concentration dependence, rationalized within MCT as the approach to its ideal-glass transition temperature Tc. The Darken equation relating self- and interdiffusion qualitatively reproduces the concentration dependence in both Zr-Ni and Al-Ni, but quantitatively, the kinetic contributions to interdiffusion can be slower than the lower bound suggested by the Darken equation. As temperature is decreased, the agreement with Darken's equation improves, due to a strong coupling of all kinetic modes that is a generic feature predicted by MCT.

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  • Received 2 May 2014
  • Revised 16 July 2014

DOI:https://doi.org/10.1103/PhysRevB.90.024309

©2014 American Physical Society

Authors & Affiliations

P. Kuhn1, J. Horbach2, F. Kargl1, A. Meyer1, and Th. Voigtmann1,3

  • 1Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 51170 Köln, Germany
  • 2Soft Matter Laboratory, IPKM, Heinrich-Heine Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany
  • 3Department of Physics, Heinrich-Heine Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany

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Vol. 90, Iss. 2 — 1 July 2014

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