Thiophene thiol on the Au(111) surface: Size-dependent adsorption study

摘要

The adsorption of the thiophene-2-thiolate and thiophen-2-yl-methanethiolate radicals has been investigated on the Au(111) surface using density functioanl theory under the framework of the generalized gradient approxiamtion for the exchange-correaltion functions. In order to underscore the quantum size effects on the adsorption geometry, the Au(111) surface was modeled using a finite-sized clsuter (Au_3 and Au_(24)) truncated from the surface as well as a periodic slab consisting of 100 atoms. The results reveal that the preferential adsorption site differs for the cluster models and slab approaches. The directioanl nature of the Au-S bond and the influence of the back bond of the terminal sulfur atom are found to play key roles in the adsorption geometry. The adsorption energies suggest that the binding neergies for the clsuter models are stronger than the slab. Inclusion of an alkyl group in between the thiophene ring and the thiol group enhances the interaction energies of the gold-sulfur bonds.