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The European Physical Journal B
ISSN: 1434-6028 (printed version)
ISSN: 1434-6036 (electronic version)
Abstract Volume 1 Issue 4 (1998) pp 523-531
Diffusion of adsorbates on random alloy surfaces
F. Nieto (1) (a), C. Uebing (1)(2) (b)
(1) Max-Planck-Institut für Eisenforschung, 40074 Düsseldorf, Germany
(2) Lehrstuhl für Physikalische Chemie II, Universität Dortmund, 44227 Dortmund, Germany
Received: 24 October 1997 / Accepted: 17 December 1997
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.
PACS. 68.35.Fx Diffusion; interface formation - 68.35.Bs Surface structure and topography - 68.35.-p Solid surfaces and solid-solid interfaces
(a) Permanent address: Departamento de Física and Centro Latinoamericano de Estudios Ilya Prigogine, Universidad Nacional de San Luis, CONICET, Chacabuco 917, 5700 San Luis, Argentina
(b) email: uebing@mpie-duesseldorf.mpg.de
Online publication: March 19, 1998
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