Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 41: Inorganic/Organic Interfaces
O 41.32: Poster
Dienstag, 17. März 2015, 18:15–21:00, Poster B
Including depolarization effects in molecular dynamics simulations of self-assembled monolayers — •Iris Hehn1, Manuel Vieider1, Otello M. Roscioni2, Swen Schuster3, Michael Zharnikov3, Claudio Zannoni2, and Egbert Zojer1 — 1Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Austria — 2Dipartimento di Chimica Industriale "Toso Montanari", Università di Bologna, Italy — 3Applied Physical Chemistry, Heidelberg University, Germany
In a regular, ordered arrangement of molecules with aligned electric dipole moments depolarization effects take place and the individual molecular dipoles get reduced. This effect can be quite significant often reducing dipole moments to a small fraction of their original values. Depolarization should also be considered, when determining the non-bonding Coulomb interactions in molecular dynamics (MD) simulations, which are, however, typically based on calculating atomic charges of isolated molecules. Instead, to account for the depolarization we calculate the atomic charges for a molecule surrounded by a cluster of point charges that reproduces the electric field in the self-assembled monolayer (SAM), where the embedding charge distribution has to be determined self-consistently. In a second self-consistency cycle also the geometry of the molecules in the SAM is optimized considering the depolarized charge distribution in the MD runs. We test our approach on SAMs consisting of cyano-substituted biphenylthiol and a mid-chain ester functionalized alkanethiol, which differ both in the rigidity of the backbones and the orientation and location of the dipoles.