Density Profile Evolution and Nonequilibrium Effects in Partial and Full Spreading Measurements of Surface Diffusion

dc.contributorAalto Universityen
dc.contributor.authorNikunen, P.
dc.contributor.authorVattulainen, Ilpo
dc.contributor.authorAla-Nissilä, Tapio
dc.contributor.departmentDepartment of Applied Physicsen
dc.contributor.departmentTeknillisen fysiikan laitosfi
dc.contributor.schoolPerustieteiden korkeakoulufi
dc.contributor.schoolSchool of Scienceen
dc.description.abstractWe study the nature of nonequilibrium effects in the collective diffusion coefficient DC(θ) vs the coverage θ as extracted from Boltzmann–Matano analysis of spreading coverage profiles. We focus on the temporal behavior of the profiles and study how the corresponding nonequilibrium effects in DC(θ) depend on the initial density gradient and the initial state from which the spreading starts. To this end, we carry out extensive Monte Carlo simulations for a lattice-gas model of the O/W(110) system. Studies of submonolayer spreading from an initially ordered p(2×1) phase at θ=12 reveal that the spreading and diffusion rates in directions parallel and perpendicular to rows of oxygen atoms are significantly different within the ordered phase. Aside from this effect, we find that the degree of ordering in the initial phase has a relatively small impact on the overall behavior of DC(θ). Also, although we find that nonequilibrium effects are clearly present in submonolayer spreading profiles, DC(θ) determined from such data approaches its asymptotic equilibrium behavior much more rapidly than in the case of full spreading. Nevertheless, in both cases there are noticeable deviations from equilibrium results that persist even at very long times and are strongest in ordered phases and in the vicinity of phase boundaries. These conclusions are confirmed by complementary studies of the temporal behavior of the order parameter φ(θ). Finally, we use DC(θ) and φ(θ) to determine the locations of phase boundaries and find such data to be clearly time dependent during full spreading. We conclude that nonequilibrium effects seem to be an inherent feature in profile evolution studies of surface diffusion in all cases where ordering plays a prominent role. This warrants particular care to be taken with profile spreading experiments.en
dc.description.versionPeer revieweden
dc.identifier.citationNikunen, P. & Vattulainen, I. & Ala-Nissilä, Tapio. 2001. Density Profile Evolution and Nonequilibrium Effects in Partial and Full Spreading Measurements of Surface Diffusion. The Journal of Chemical Physics. Volume 114, Issue 14. P. 6335-6345. ISSN 1089-7690 (electronic). ISSN 0021-9606 (printed). DOI: 10.1063/1.1355765.en
dc.identifier.issn1089-7690 (electronic)
dc.identifier.issn0021-9606 (printed)
dc.publisherAIP Publishingen
dc.relation.ispartofseriesThe Journal of Chemical Physicsen
dc.relation.ispartofseriesVolume 114, Issue 14
dc.rights© 2001 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.
dc.rights.holderAmerican Institute of Physics
dc.subject.keywordcollective effectsen
dc.subject.keywordMonte Carlo methodsen
dc.subject.keywordsurface measurementsen
dc.subject.keywordsurface diffusionen
dc.subject.keywordprofile spreadingen
dc.subject.keywordadsorbate dynamicsen
dc.titleDensity Profile Evolution and Nonequilibrium Effects in Partial and Full Spreading Measurements of Surface Diffusionen
dc.typeA1 Alkuperäisartikkeli tieteellisessä aikakauslehdessäfi
dc.type.versionFinal published versionen
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