Diffusion of hard disks and rodlike molecules on surfaces
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© 2001 American Physical Society (APS). http://www.aps.org
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Date
2001
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Language
en
Pages
021204/1-7
Series
Physical Review E, Volume 64, Issue 2
Abstract
We study the submonolayer diffusion of hard disks and rodlike molecules on smooth surfaces through numerical simulations and theoretical arguments. We concentrate on the behavior of the various diffusion coefficients as a function of the two-dimensional (2D) number density ρ in the case where there are no explicit surface-particle interactions. For the hard disk case, we find that while the tracer diffusion coefficient DT(ρ) decreases monotonically up to the freezing transition, the collective diffusion coefficient DC(ρ) is wholly determined by the inverse compressibility which increases rapidly on approaching freezing. We also study memory effects associated with tracer diffusion, and present theoretical estimates of DT(ρ) from the mode-mode coupling approximation. In the case of rigid rods with short-range repulsion and no orientational ordering, we find behavior very similar to the case of disks with the same repulsive interaction. Both DT(ρ) and the angular diffusion coefficient DR(ρ) decrease with ρ. Also in this case DC(ρ) is determined by inverse compressibility and increases rapidly close to freezing. This is in contrast to the case of flexible chainlike molecules in the lattice-gas limit, where DC(ρ) first increases and then decreases as a function of the density due to the interplay between compressibility and mobility.Description
Keywords
surface diffusion, Brownian motion, computer simulations
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Citation
Lahtinen, J. M. & Hjelt, T. & Ala-Nissilä, Tapio & Chvoj, Z. 2001. Diffusion of hard disks and rodlike molecules on surfaces. Physical Review E. Volume 64, Issue 2. P. 021204/1-7. ISSN 1539-3755 (printed). DOI: 10.1103/physreve.64.021204.