Conformation and Dynamics of Arylthiol Self-Assembled Monolayers on Au(111)

T. E. Dirama and J. A. Johnson, Langmuir, 23(24), 12208-12216 (2007).

We report a computational investigation of the conformation and the = dynamics of self-assembled monolayers (SAMs) of a set of aromatic thiols = arranged in the ( 3 =D7 3)-R30 packing ratio on a Au(111) surface using = molecular dynamics (MD) simulations. It was found that the molecular = conformations were better defined for the arylthiol with two phenyl = groups as compared to those with a single phenyl group and that the = chemical structure of the head and tail groups had a considerable = influence on the system geometry. In line with the density functional = theory (DFT) calculations of small thiol molecules, we found for the = SAMs that the face-centered cubic (fcc) site on the Au(111) surface was = the most preferred, followed by the hexagonal close-packed (hcp) site, = while the bridge position showed the characteristics of a local energy = maximum. The dynamics of thiol head groups on these three Au sites was = found to govern the overall dynamics of SAMs as measured by the mean = square displacement. We also report that both the conformation and the = dynamics on the studied time scale were driven by the SAM formation = energy.

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