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

TL;DR

This study uses density functional theory to analyze how van der Waals forces influence the adsorption energies, geometries, and electronic interactions of isooctane and ethanol on Fe(100) surfaces, highlighting their essential role.

Contribution

It demonstrates the importance of vdW interactions in adsorption processes on Fe(100) surfaces using various exchange-correlation functionals within DFT.

Findings

vdW forces increase adsorption energies

vdW forces reduce equilibrium distances

vdW forces do not alter molecular spatial configuration

Abstract

Van der Waals (vdW) forces play a fundamental role in the structure and behavior of diverse systems. Thanks to development of functionals that include non-local 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 a 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 non-isotropic, 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.