title: Density Functional Investigation of the Adsorption of Isooctane, Ethanol, and Acetic Acid on a Water-Covered Fe(100) Surface.
abstract: The presence of water in biofuels poses the question of how it affects the frictional performance of additives in fuels containing organic substances. To investigate the effect of water on the adsorption of molecules present in fuel and its additives we simulated within the framework of density functional theory the adsorption of ethanol, isooctane (2,2,4-trimethylpentane), and acetic acid on a bare and a water-covered Fe(100) surface. Van der Waals interactions are taken into account in our computations. In those molecules, where dispersion forces contribute significantly to the binding mechanism, the water layer has a stronger screening effect. Additionally, this effect can be enhanced by the presence of polar functional groups in the molecule. Thus, with the introduction of a water layer, the adsorption energy of isooctane and ethanol is reduced but it is increased in the case of the acetic acid. The adsorption configuration of ethanol is changed, while the one of acetic acid is moderately, and for isooctane only very slightly altered. Therefore, the effect of a water layer in the adsorption of organic molecules on an Fe(100) surface strongly depends on the type of bond and consequently, so do the tribological properties.
authors.affiliation: Institute of Applied Physics, Vienna University of Technology , Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria ; Austrian Center of Competence for Tribology, Viktor-Kaplan-Strasse 2, 2700 Wiener Neustadt, Austria.
authors.forename: Pedro O
authors.initials: PO
authors.lastname: Bedolla
authors.affiliation: Institute of Applied Physics, Vienna University of Technology , Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria ; Austrian Center of Competence for Tribology, Viktor-Kaplan-Strasse 2, 2700 Wiener Neustadt, Austria.
authors.forename: Gregor
authors.initials: G
authors.lastname: Feldbauer
authors.affiliation: Institute of Applied Physics, Vienna University of Technology , Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria ; Austrian Center of Competence for Tribology, Viktor-Kaplan-Strasse 2, 2700 Wiener Neustadt, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Wolloch
authors.affiliation: Institute of Applied Physics, Vienna University of Technology , Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria.
authors.forename: Christoph
authors.initials: C
authors.lastname: Gruber
authors.affiliation: Austrian Center of Competence for Tribology, Viktor-Kaplan-Strasse 2, 2700 Wiener Neustadt, Austria.
authors.forename: Stefan J
authors.initials: SJ
authors.lastname: Eder
authors.affiliation: Austrian Center of Competence for Tribology, Viktor-Kaplan-Strasse 2, 2700 Wiener Neustadt, Austria.
authors.forename: Nicole
authors.initials: N
authors.lastname: Dörr
authors.affiliation: Institute of Applied Physics, Vienna University of Technology , Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Mohn
authors.affiliation: Institute of Applied Physics, Vienna University of Technology , Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria.
authors.forename: Josef
authors.initials: J
authors.lastname: Redinger
authors.affiliation: Institute of Applied Physics, Vienna University of Technology , Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria ; Austrian Center of Competence for Tribology, Viktor-Kaplan-Strasse 2, 2700 Wiener Neustadt, Austria.
authors.forename: András
authors.initials: A
authors.lastname: Vernes