title: Effects of van der Waals Interactions in the Adsorption of Isooctane and Ethanol on Fe(100) Surfaces.
abstract: van der Waals (vdW) forces play a fundamental role in the structure and behavior of diverse systems. Because of development of functionals that include nonlocal correlation, it is possible to study the effects of vdW interactions in systems of industrial and tribological interest. Here we simulated within the framework of density functional theory (DFT) the adsorption of isooctane (2,2,4-trimethylpentane) and ethanol on an Fe(100) surface, employing various exchange-correlation functionals to take vdW forces into account. In particular, this paper discusses the effect of vdW forces on the magnitude of adsorption energies, equilibrium geometries, and their role in the binding mechanism. According to our calculations, vdW interactions increase the adsorption energies and reduce the equilibrium distances. Nevertheless, they do not influence the spatial configuration of the adsorbed molecules. Their effect on the electronic density is a nonisotropic, delocalized accumulation of charge between the molecule and the slab. In conclusion, vdW forces are essential for the adsorption of isooctane and ethanol on a bcc Fe(100) surface.
authors.affiliation: Institute of Applied Physics, Vienna University of Technology , Wiedner Hauptstraße 8-10/134, 1040 Vienna, Austria ; Austrian Center of Competence for Tribology (AC2T Research GmbH), 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 (AC2T Research GmbH), 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 (AC2T Research GmbH), Viktor-Kaplan-Straße 2, 2700 Wiener Neustadt, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Wolloch
authors.affiliation: Austrian Center of Competence for Tribology (AC2T Research GmbH), 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 (AC2T Research GmbH), 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 (AC2T Research GmbH), Viktor-Kaplan-Straße 2, 2700 Wiener Neustadt, Austria.
authors.forename: András
authors.initials: A
authors.lastname: Vernes