title: Van der Waals interactions and the limits of isolated atom models at interfaces.
abstract: Van der Waals forces are among the weakest, yet most decisive interactions governing condensation and aggregation processes and the phase behaviour of atomic and molecular matter. Understanding the resulting structural motifs and patterns has become increasingly important in studies of the nanoscale regime. Here we measure the paradigmatic van der Waals interactions represented by the noble gas atom pairs Ar-Xe, Kr-Xe and Xe-Xe with a Xe-functionalized tip of an atomic force microscope at low temperature. Individual rare gas atoms were fixed at node sites of a surface-confined two-dimensional metal-organic framework. We found that the magnitude of the measured force increased with the atomic radius, yet detailed simulation by density functional theory revealed that the adsorption induced charge redistribution strengthened the van der Waals forces by a factor of up to two, thus demonstrating the limits of a purely atomic description of the interaction in these representative systems.
authors.affiliation: International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1, Namiki, Tsukuba, 305-0044 Ibaraki, Japan.|Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.|Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, 4-1-8, Honcho, Kawaguchi, 332-0012 Saitama, Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Kawai
authors.affiliation: COMP, Department of Applied Physics, Aalto University, PO Box 11100, FI-00076 Aalto, Finland.|Division of Electrical Engineering and Computer Science, Kanazawa University, Kanazawa 920-1192, Japan.
authors.forename: Adam S
authors.identifier: 0000-0001-5371-5905
authors.initials: AS
authors.lastname: Foster
authors.affiliation: COMP, Department of Applied Physics, Aalto University, PO Box 11100, FI-00076 Aalto, Finland.|Physics/Department of Natural Sciences, Åbo Akademi University, 20500 Turku, Finland.
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Björkman
authors.affiliation: Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
authors.forename: Sylwia
authors.initials: S
authors.lastname: Nowakowska
authors.affiliation: Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping 58183, Sweden.
authors.forename: Jonas
authors.initials: J
authors.lastname: Björk
authors.affiliation: COMP, Department of Applied Physics, Aalto University, PO Box 11100, FI-00076 Aalto, Finland.|Aalto Science Institute, Aalto University, PO Box 15500, FI-00076 Aalto, Finland.
authors.forename: Filippo Federici
authors.initials: FF
authors.lastname: Canova
authors.affiliation: Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany.
authors.forename: Lutz H
authors.initials: LH
authors.lastname: Gade
authors.affiliation: Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.|Laboratory for Micro- and Nanotechnology, Paul Scherrer Institute, CH-5232 Villigen, Switzerland.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Jung
authors.affiliation: Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.
authors.forename: Ernst
authors.initials: E
authors.lastname: Meyer