Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 95: Metal Substrates: Adsorption of Atoms and Inorganic Molecules

O 95.4: Vortrag

Donnerstag, 23. März 2017, 16:00–16:15, WIL A317

DFT study of water at the stoichiometric and defected Fe(110) surfaces — •Tomasz Ossowski1, Juarez L.F. Da Silva1,2, and Adam Kiejna11Institute of Experimental Physics, University of Wrocław, Poland — 2Instituto de Química de São Carlos, Universidade de São Paulo, Brazil

Water adsorption on iron surfaces is important in understanding of corrosion and reduction of iron oxides by hydrogen. Density functional theory (DFT) with van der Waals correction is applied to study molecular water adsorption on stoichiometric and defected Fe(110) surfaces. Structural and electronic properties of the H2O/Fe(110) system, and a role of the vacancies are analysed. Results show that vacancy prefers sites at the topmost atomic layer, without energy barrier for its diffusion from the interior. The vacancies cause decreasing of the work function and local change the geometry with larger effects for higher vacancy density. At stoichiometric surface water adsorbs flat on top the Fe atoms with the H-O-H plane parallel to the surface, with binding energy of about 0.3 eV/molecule. Moreover, the adsorption energy of flat lying water is degenerated for few different orientation. It suggests possibility of H2O rotation around direction perpendicular to the surface. At the defected surface, H2O prefers sites near the vacancy. The binding of water to defected surface is by more than 0.2 eV stronger than to the stoichiometric one. Moreover, the adsorption of H2O at stoichiometric region of the defected surface is by about 0.2 eV less preferable. It means that water is stronger bound to defected Fe(110) surface and vacancy can be considered as an adsorption centre for H2O.

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