Role of van der Waals forces in the adsorption and diffusion of organic molecules on an insulating surface

Abstract

All material supplied via Aaltodoc is protected by copyright and other intellectual property rights, and duplication or sale of all or part of any of the repository collections is not permitted, except that material may be duplicated by you for your research use or educational purposes in electronic or print form. You must obtain permission for any other use. Electronic or print copies may not be offered, whether for sale or otherwise to anyone who is not an authorised user. The adsorption and diffusion of 3,4,9,10-perylene-tetracarboxylic-dianhydride ͑PTCDA͒ molecules on a nanostructured KBr ͑001͒ surface were investigated by combining noncontact atomic force microscopy ͑NC-AFM͒ and first-principles calculations. Atomically resolved measurements demonstrate trapping of PTCDA molecules in intentionally created rectangular monolayer-deep substrate pits and a preferential adsorption at kink sites. In order to understand the experimental results, we found that it was essential to include a firstprinciples treatment of the van der Waals interactions. We show that at some sites on the surface, 85% of the molecular binding is provided by van der Waals interactions, and in general it is always the dominant contribution to the adsorption energy. It also qualitatively changes molecular diffusion on the surface. Based on the specificity of the molecular interaction at kink sites, the species of the imaged ionic sublattice in the NC-AFM measurements could be identified.

Role of van der Waals interaction in forming molecule-metal junctions: flat organic molecules on the Au(111) surface

“…These limitations have been recently overcome [57][58][59] and the fully self-consistent vdW-DF calculations with complete geometry relaxation can now be performed routinely on systems consisting of hundreds of atoms. Here for the first time we report such calculations on a number of flat organic molecules adsorbed on the Au(111) surface with the aim of guiding the theoretical effort required to investigate supramolecular assemblies on flat metal surfaces.…”

Measuring Electric Field Induced Subpicometer Displacement of Step Edge Ions

“…The cleaved bulk surfaces often exhibit large and atomically flat terraces bounded by monoatomic step edges. In particular, the geometry and potential variations near step edges play a main role in growth and etching of crystals [11,12], adsorption of molecules [13][14][15] and metallic nanoclusters [16], including the diffusion and pinning dynamics of adsorbates [17,18], and friction [19,20]. It is well known that atomic interaction increases due to the low coordination of the step ions [21], forming an Ehrlich-Schwoebel-like barrier [22].…”

Van der Waals interactions between graphitic nanowiggles

“…The van der Waals interaction, arising from the quantum fluctuations within bodies, has received enthusiastic attention in recent years due to its important role from condensed matter physics [1][2][3] to biological systems [4,5]. At nanoscale, this force is much more dominant than other forces such as the electromagnetic force [6].…”