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Effects of van der Waals Interactions in the Adsorption of Isooctane and Ethanol on Fe(100) Surfaces.

Bedolla PO, Feldbauer G, Wolloch M, Eder SJ, Dörr N, Mohn P, Redinger J, Vernes A - J Phys Chem C Nanomater Interfaces (2014)

Bottom Line: van der Waals (vdW) forces play a fundamental role in the structure and behavior of diverse systems.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.

View Article: PubMed Central - PubMed

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.

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.

No MeSH data available.


Calculated adsorptionenergy of an ethanol molecule on the bccFe(100) surface as a function of the vertical distance for the PBE,revPBE, revPBE+LDA, vdW-DF, and optB86b-vdW exchange–correlationpotentials.
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fig8: Calculated adsorptionenergy of an ethanol molecule on the bccFe(100) surface as a function of the vertical distance for the PBE,revPBE, revPBE+LDA, vdW-DF, and optB86b-vdW exchange–correlationpotentials.

Mentions: As in the case of isooctane, thenonlocal correlation enhancesthe binding energy between the adsorbed ethanol molecule and the bccFe(100) surface (Table 1). The adsorption energycalculated with the optB86b-vdW functional is only 2 times largerthan the one calculated with the PBE functional, and the equilibriumseparation is 2.00 Å in both cases (Figure 8). This difference is remarkably smaller than the one in the adsorptionof isooctane and can be caused either by the involvement of otherforces in the binding mechanism or by an artifact, as in the LDA functional.To investigate these possibilities, the effect of the long-range interactionsis extracted by comparing calculations with the vdW-DF functionalto calculations with revPBE+LDA, as previously described. The contributionto the adsorption energy which can be attributed to the dispersionforces is 95% (Figure 8). Although this showsa significant contribution of the nonlocal interactions to the bindingmechanism, the difference of 278 meV between the adsorption energiescalculated with the vdW-DF and the optB86b-vdW functional needs tobe investigated before discarding the contribution of other forcesto the adsorption energy.


Effects of van der Waals Interactions in the Adsorption of Isooctane and Ethanol on Fe(100) Surfaces.

Bedolla PO, Feldbauer G, Wolloch M, Eder SJ, Dörr N, Mohn P, Redinger J, Vernes A - J Phys Chem C Nanomater Interfaces (2014)

Calculated adsorptionenergy of an ethanol molecule on the bccFe(100) surface as a function of the vertical distance for the PBE,revPBE, revPBE+LDA, vdW-DF, and optB86b-vdW exchange–correlationpotentials.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126734&req=5

fig8: Calculated adsorptionenergy of an ethanol molecule on the bccFe(100) surface as a function of the vertical distance for the PBE,revPBE, revPBE+LDA, vdW-DF, and optB86b-vdW exchange–correlationpotentials.
Mentions: As in the case of isooctane, thenonlocal correlation enhancesthe binding energy between the adsorbed ethanol molecule and the bccFe(100) surface (Table 1). The adsorption energycalculated with the optB86b-vdW functional is only 2 times largerthan the one calculated with the PBE functional, and the equilibriumseparation is 2.00 Å in both cases (Figure 8). This difference is remarkably smaller than the one in the adsorptionof isooctane and can be caused either by the involvement of otherforces in the binding mechanism or by an artifact, as in the LDA functional.To investigate these possibilities, the effect of the long-range interactionsis extracted by comparing calculations with the vdW-DF functionalto calculations with revPBE+LDA, as previously described. The contributionto the adsorption energy which can be attributed to the dispersionforces is 95% (Figure 8). Although this showsa significant contribution of the nonlocal interactions to the bindingmechanism, the difference of 278 meV between the adsorption energiescalculated with the vdW-DF and the optB86b-vdW functional needs tobe investigated before discarding the contribution of other forcesto the adsorption energy.

Bottom Line: van der Waals (vdW) forces play a fundamental role in the structure and behavior of diverse systems.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.

View Article: PubMed Central - PubMed

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.

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.

No MeSH data available.