State-of-the-art first principles calculations based on density functional theory were performed on CH 3 (CH 2 ) n−1 S-Au(111) systems. We show that the adsorption site of methylthiolate at low coverage on the Au(111) surface is the fcc site, not the hcp site as has been recently reported. Further, we report results for chain length dependency and the electronic structure of the system.The interaction between organic materials and solid surfaces has been extensively studied because of the broad range of industrial applications. 1-4 Self-assembled monolayers (SAMs) hold special interest, because the presence of the thiol group greatly strengthens the molecule-surface interactions, inducing order in the layer. SAMs have important potential applications in industry, such as sensors, transducers, detectors, packaging and insulating layers for integrated circuits, functionalization of surfaces, thin coatings for electrodes, and corrosion inhibition.The long-chain alkane thiols [CH 3 (CH 2 ) n−1 SH, or C n ] form SAMs on the Au(111) surface. Their simplicity, highly ordered structures, and chemical stability make these systems ideal for study with a variety of techniques including atomic force microscopy, 5,6 infrared spectroscopy, 7,8 high-resolution electron-energy-loss spectroscopy, 9 grazing X-ray diffraction, 10 scanning tunneling microscopy (STM), 11-17 scanning probe microscopy, 18 lowenergy electron diffraction (LEED), [19][20][21] He atom diffraction, 22,23 and theory. 25-31 Despite 1
