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          Institute: Fritz-Haber-Institut     Collection: Inorganic Chemistry     Display Documents

ID: 346845.0, Fritz-Haber-Institut / Inorganic Chemistry
Surface structure and water adsorption on Fe3O4(111): Spin-density functional theory and on-site Coulomb interactions
Authors:Grillo, Maria Elena; Finnis, Mike W.; Ranke, Wolfgang
Research Context:ac19: Iron oxide model catalysts, Adsorption and catalysis
Date of Publication (YYYY-MM-DD):2008-02-15
Title of Journal:Physical Review B
Journal Abbrev.:Phys. Rev. B
Issue / Number:7
Start Page:075407-1
End Page:075407-2
Review Status:Peer-review
Audience:Experts Only
Intended Educational Use:No
Abstract / Description:The surface structure of magnetite Fe3O4(111) in contact with oxygen and water is investigated using spin density functional theory plus on-site Coulomb interactions. The present results unravels apparent contradictions in the experimental data regarding the equilibrium stoichiometry of the bare surface termination. Both for 298 K and 1200 K, the equilibrium structure is terminated by 1/4 monolayer (ML) of iron (Fe) on top of a full oxygen layer, consistent with an earlier low-energy electron diffraction analysis. Nontheless, the calculated negative slope of the surface energies vs oxygen partial pressure shows that a 1/2 ML Fe termination would become stable under oxygen poor conditions at high temperatures, in agreement to interpretation of scanning tunneling microscopy experiments. Initial water adsorption is dissociative and saturates when all Fe sites are occupied by OH groups while the H atoms bind to surface oxygen. Further water bridges the OH and H groups resulting in a quite unique type of H-bonded molecular water with its oxygen forming a hydronium ion like structure OH3+-OH. This water structure is different from the water dimeric structures found as yet on oxide and metal surfaces for partially dissociated (H2O-OH-H) overlayers.
Last Change of the Resource (YYYY-MM-DD):2007-12-20
External Publication Status:published
Document Type:Article
Communicated by:Robert Schlögl
Affiliations:Fritz-Haber-Institut/Inorganic Chemistry/Surface Analysis
External Affiliations:Centro de Quimica IVIC, Apartado 21827 Caracas 1020 A, Venezuela,
Department of Materials, Imperial College, 46812 Exhibition Road, London SW7 2AZ, United Kingdom
URL:http://dx.doi.org/10.1103/PhysRevB.77.075407 [doi]
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