Vladimirova M, Trimarchi G, Baldereschi A, Weckesser J, Kern K, Barth JV, De Vita A

We model the geometry. binding site and absolute orientation of the self-assembled monolayer of 4-[pyrid-4-yl-ethynyl] benzoic acid (PEBA) adsorbed on the (1 1 1) Surface of silver by means of molecular dynamics and first principles calculations, and compare these results With those we obtain from scanning tunneling microscopy experiments. Our results indicate that the adsorbate-substrate interaction controls the overall orientation of the self-assembled molecular Superstructures. We investigate the nature of this interaction, which is found to induce some degree of readjustment of the molecular structure and Substantial stretching of the intermolecular hydrogen bonds. This is consistent with the nodal Structure of the interaction-induced ab initio differential charge density, which can be interpreted in terms of a simple extended Huckel model. (C) 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.