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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 adsorption energy of an isooctane molecule on the bccFe(100) surface as a function of the vertical distance for the PBE,revPBE+LDA, vdW-DF, and optB86b-vdW exchange–correlation potentials.
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fig3: Calculated adsorption energy of an isooctane molecule on the bccFe(100) surface as a function of the vertical distance for the PBE,revPBE+LDA, vdW-DF, and optB86b-vdW exchange–correlation potentials.

Mentions: Nonlocal interactions increase the adsorptionenergy of isooctaneon a bcc Fe(100) surface and reduce the equilibrium distance (Table 1). The absolute value of the adsorption energy calculatedwith the optB86b-vdW functional is more than 12 times larger thanthe one calculated with the PBE functional, while the distance betweenthe slab and the molecule, when in equilibrium, is reduced by 1.00Å (Figure 3). To investigate the contributionof the nonlocal correlation to this increment, we compared the adsorptionenergies calculated with the vdW-DF and the revPBE+LDA functionals.The resulting energy difference is then 418 meV (Figure 3). Since this difference accounts for 95.8% of the adsorptionenergy calculated with the vdW-DF functional, the variation can nowbe unambiguously attributed to the dispersion forces. By the samereasoning, the decrease in the binding distance of 1.50 Å canalso be associated with nonlocal interactions.


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

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

fig3: Calculated adsorption energy of an isooctane molecule on the bccFe(100) surface as a function of the vertical distance for the PBE,revPBE+LDA, vdW-DF, and optB86b-vdW exchange–correlation potentials.
Mentions: Nonlocal interactions increase the adsorptionenergy of isooctaneon a bcc Fe(100) surface and reduce the equilibrium distance (Table 1). The absolute value of the adsorption energy calculatedwith the optB86b-vdW functional is more than 12 times larger thanthe one calculated with the PBE functional, while the distance betweenthe slab and the molecule, when in equilibrium, is reduced by 1.00Å (Figure 3). To investigate the contributionof the nonlocal correlation to this increment, we compared the adsorptionenergies calculated with the vdW-DF and the revPBE+LDA functionals.The resulting energy difference is then 418 meV (Figure 3). Since this difference accounts for 95.8% of the adsorptionenergy calculated with the vdW-DF functional, the variation can nowbe unambiguously attributed to the dispersion forces. By the samereasoning, the decrease in the binding distance of 1.50 Å canalso be associated with nonlocal interactions.

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.