A Density Functional Theory Investigation of Carboranethiol Self-Assembled Monolayer on Au(111)

TL;DR

This study uses density functional theory to analyze how different carboranethiol isomers adsorb on gold surfaces, revealing how molecular dipole orientation influences binding, electronic properties, and preferred surface structures.

Contribution

It provides the first detailed theoretical analysis of carboranethiol monolayer adsorption on gold, highlighting the role of dipole moments and identifying the most stable surface configurations.

Findings

Adsorption favors isomers with dipoles parallel to the surface.

The (5×5) unit cell is more stable than the (√19×√19)R23.4° structure.

Binding energy correlates with molecular dipole moments.

Abstract

Isolated and full monolayer adsorption of various carboranethiol (C$_2$B$_{10}$H$_{12}$S) isomers on gold (111) surface have been investigated using both the standard and van der Waals density functional theoretical calculations. The effect of differing molecular dipole moment orientations on the low energy adlayer geometries, the binding characteristics and the electronic properties of the self-assembled monolayers of these isomers have been studied. Specifically, the binding energy and work function changes associated with different molecules show a correlation with their dipole moments. The adsorption is favored for the isomers with dipole moments parallel to the surface. Of the two possible unit cell structures, the (5$\times$5) was found to be more stable than the ($\sqrt{19}\times\sqrt{19}$)R23.4$^o$ one.