c(4 × 2) Structures of Alkanethiol Monolayers on Au (111) Compatible with the Constraint of Dense Packing

Using alkanethiol dense packing as a starting point, we have found [O. Voznyy and J.J. Dubowski, Langmuir 25(13), 7353 (2009)] six prototypical packing structures commensurate with the (3 × 2√3) supercell of the Au (111) surface. Five of the six structures are not compatible with the flat surface conditions but can be fitted to a reconstructed surface. Combined with density functional theory calculations and simulations of grazing incidence X-ray diffraction maps and of scanning tunneling microscopy images, this allowed us to refine and assess the recently proposed models of the c(4 × 2) self-assembled monolayers involving thiolate−adatom and thiolate−adatom−thiolate species and to propose a new model with four gold adatoms per unit cell.
© 2009 American Chemical Society. [DOI: 10.1021/la8043347]

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