title: Sulfur dimers adsorbed on Au(111) as building blocks for sulfur octomers formation: A density functional study.
abstract: Experimental scanning tunneling microscopy (STM) studies have shown for more than two decades rectangular formations when sulfur atoms are deposited on Au(111) surfaces. The precursors have ranged from simple molecules or ions, such as SO2 gas or sulfide anions, to more complex organosulfur compounds. We investigated, within the framework of the Density Functional Theory, the structure of these rectangular patterns assuming them entirely composed of sulfur atoms as the experimental evidence suggests. The sulfur coverage at which the simulations were carried out (0.67 ML or higher) provoked that the sulfur-sulfur association had to be taken into account for achieving a good agreement between the sets of simulated and experimental STM images. A combination of four sulfur dimers per rectangular formation properly explained the trends obtained by the experimental STM analysis which were related with the rectangles' size and shape fluctuations together with sulfur-sulfur distances within these rectangles. Finally, a projected density of states analysis showed that the dimers were capable of altering the Au(5d) electronic states at the same level as atomic sulfur adsorbed at low coverage. Besides, sulfur dimers states were perfectly distinguished, whose presence near and above the Fermi level can explain both: sulfur-sulfur bond elongation and dimers stability when they stayed adsorbed on the surface at high coverage.
authors.affiliation: Laboratory of Computational and Theoretical Chemistry (LQCT), Faculty of Chemistry, Havana University, Havana 10400, Cuba.
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Hernandez-Tamargo
authors.affiliation: Laboratory of Computational and Theoretical Chemistry (LQCT), Faculty of Chemistry, Havana University, Havana 10400, Cuba.
authors.forename: Ana Lilian
authors.initials: AL
authors.lastname: Montero-Alejo
authors.affiliation: Higher Institute of Technologies and Applied Sciences (InSTEC), Havana 10400, Cuba.
authors.forename: Daniel Codorniu
authors.initials: DC
authors.lastname: Pujals
authors.affiliation: Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9/E164-EC, 1060 Vienna, Austria.
authors.forename: Hans
authors.initials: H
authors.lastname: Mikosch
authors.affiliation: Instituto de Ciencias y Tecnologías de Materiales (IMRE), Havana 10400, Cuba.
authors.forename: Mayra P
authors.initials: MP
authors.lastname: Hernández