A van der Waals DFT study of chain length dependence of alkanethiol adsorption on Au(111): physisorption vs. chemisorption

Abstract

The energetics and structures of physisorbed and chemisorbed alkanethiols on Au(111) have been systematically investigated up to 10 carbon atoms using van der Waals (vdW) corrected density functional theory (DFT) calculations. The role of chain length, tilting angle and coverage on the adsorption characteristics has been examined to elucidate the energetics and plausible transformation mechanisms between lying down and standing up phases. Coverage and size dependent chain-chain electronic interactions counteract with the alkyl chain-gold surface interactions and the surface relaxation of the metal in the formation of standing up monolayer structures. For the striped phases of long chain alkanethiols, however, our calculations on decanethiol indicate alkyl chain-gold surface interactions to be strong enough to force the molecule to be perfectly parallel to the surface by lifting a gold atom up, in agreement with the proposed models for this film in the literature.

Identifying key descriptors in surface binding: interplay of surface anchoring and intermolecular interactions for carboxylates on Au(110)

“…The overall hierarchy of stability for carboxylates depends on their condensation into islands, rendering longer-chain carboxylates more stable as shown for assembly of alkanethiols on Au(111) for carbon chains up to ten carbons. 53 Accordingly, adsorbate–adsorbate stabilization calculated for trifluoroacetate is the same as for acetate, consistent with a driving force for trifluoroacetate to form dense c (2 × 2) molecular domains at low coverage and in agreement with the STM results that are similar to those for acetate. The attraction occurs despite the higher electron density that could lead to larger repulsive coulombic interactions.…”

Bundling of Nanowires Induced by Unbound Ligand

“…Thermodynamic data indicates a free energy of adsorption for OAm on Au of Δ G ads = −8.1 kJ/mol (see details in the Supporting Infomration). ,− Assuming equilibrium between unbound and adsorbed OAm and using the above numbers suggest that agglomeration was induced at a grafting density of about 90% corresponding to 4.1 ligands/nm 2 .…”

Revealing the Interplay Between Covalent and Non-Covalent Interactions Driving the Adsorption of Monosubstituted Thiourea Derivatives on the Au(111) Surface

“…[44][45][46] Previous studies have proved the efficiency of the dDsC approach in the description of inter-and intramolecular forces. 46,47 Furthermore, the dDsC scheme yields a more reliable lattice parameter for the gold surface. 47 Thus, under the dDsC approach we attained, with a reasonable computational effort, an accurate modeling of molecule-metal interactions.…”