Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 36: Poster Session II (Metals; Nanostructures at surfaces; Surface or interface magnetism; Spin-Orbit Interaction at Surfaces; Electron and spin dynamics; Surface dynamics; Methods; Theory and computation of electronic structure)
O 36.102: Poster
Dienstag, 15. März 2011, 18:30–22:00, P4
Adsorption of Hydrazine (N2H4) on Hexagonal Ice(0001): First-Principles Investigations on the Mechanism of Chirality Changes — •Pawel Rodziewicz and Bernd Meyer — Interdisciplinary Center for Molecular Materials ICMM and Computer-Chemistry-Center CCC, University of Erlangen-Nürnberg, Germany
Surfaces can have a pronounced effect on the chiral properties of adsorbed molecules. For example, it has been observed that chiral molecules spontaneously separate into domains with different chirality or that enantiopure adsorbates are transformed into racemate mixtures by lowering of the activation barrier for chirality flips. We have used hydrazine as a simple model of a chiral molecule to study possible binding sites and flips of chirality on ice(0001) surfaces. The chemical properties of hydrazine are similar to those of water. Due to the presence of electron lone pairs and N-H groups hydrazine is simultaneously a proton acceptor and a proton donor. Density functional theory (DFT) calculations and Car-Parrinello molecular dynamics (CP-MD) simulations were used to investigate the interplay between molecule-molecule and molecule-substrate interactions. Hydrazine monomers and different enantiomers of its dimers were adsorbed on the hexagonal ice (0001) surface. The adsorbed aggregates were analyzed in terms of their coordination to the surface, with special focus on identifying hydrogen bonds. Finally, the process of chirality flips was studied using coordination constrained CP-MD simulations in order to obtain free energy barriers for rearrangements of enantiomers with Gauche A into Gauche B.