Modeling the adsorption of alkanes on an Au(111) surface

The adsorption of alkanes on a gold substrate is simulated by a simple computational scheme that combines the "glue model" for gold, a standard force field for alkanes, and a combination of the charge equilibration model and the Born-Mayer potential for their interaction. The adsorption energies of 10 short chains on the Au(111) surface are reproduced with an average error of less than 1 kcal mol(-1). The results allow extension of the use of the model to investigate the appeareance/disappeareance of ordered deposition on gold of longer alkanes. The unexpected transition to disorder occurs for chains between 18 and 26 carbon atoms and has been ascribed to the mismatch between the Au(111) lattice and the CH2 group periodicity, a feature that here is shown to hinder the formation of short, i.e., docking, C-Au distances.