Diffusion of adsorbates on random alloy surfaces |
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Authors: | F Nieto C Uebing |
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Institution: | Max-Planck-Institut für Eisenforschung, 40074, Düsseldorf, Germany
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Abstract: | In this work the diffusion of non-interacting adsorbates on a random AB alloy surface is considered. For this purpose a simple
cubic (sc), body-centered cubic (bcc) or face-centered cubic (fcc) auxiliary metal lattice is introduced. The auxiliary lattice
is truncated parallel to its (100) plane in such a way that the fourfold hollow positions of the metal surface form a regular
net of adsorption sites with square symmetry. The adsorption energy of each adsorption site is determined by its own environment,
i.e. by the numbers of direct A or B neighbors. The Monte-Carlo method has been utilized to simulate surface diffusion of adsorbates
on such energetically heterogeneous alloy surfaces and to calculate the tracer, jump and chemical diffusion coefficients.
The chemical diffusion coefficient was calculated via two different approaches: the fluctuation and the Kubo-Green method. The influence of energetical heterogeneities on the
surface diffusion is largely pronounced at low temperatures and low surface coverages, where most of the adatoms are trapped
by deep adsorption sites. It was found that at low temperatures the sequential occupation of the different types of adsorption
sites can be observed.
Received: 24 October 1997 / Accepted: 17 December 1997 |
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Keywords: | PACS 68 35 Fx Diffusion interface formation - 68 35 Bs Surface structure and topography - 68 35 -p Solid surfaces and solid-solid interfaces |
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