Adsorption and dimerisation of thiol molecules on Au(111) using a Z-matrix approach in density functional theory

Taylor & Francis
Publication Type:
Journal Article
Molecular Simulation, 2006, 32 (15), pp. 1219 - 1225
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Th adsorption energies of methanethiolate on Au(111) have been calculated using periodic density functional theory (DFT), based on the SIESTA methodology, with an internal coordination implementation for geometry input and sturcture optimisation. Both molecules are covalently boudn with interaction energies of 1.85 and 1.43 eV for methanethiolate and benzenethiolate, respectively. The preferred binding site is slightly offset from the bridge sire i both cases towards the fcc-hollow. The potential energy durfacces (PES) have depths of 0.36 and 0.22 eV, the hollow sites are local maxima in both cases, and there is not barrier to diffusion ofthe molecule at the bridge site. The corresponding dimers are weakly bound for methanethiolate and benzenthiolate, with binding energies of 0.38 and 0.16eV, respectively, and the preferred binding geometry is with the two sulphur atoms close to adjacent atop sites. The barrier to dissociation of the dimer dimethyl disulphide is estimated to like between 0.3 and 0.35eV.
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