Dresden 2009 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 33: Methods: Electronic structure theory II

O 33.6: Vortrag

Mittwoch, 25. März 2009, 11:45–12:00, SCH A316

Trapping of electrons on ice surfaces: an ab initio study — •M. Bockstedte^1,2, F. Baletto³, S. Scandolo⁴, and A. Rubio^2,5 — ¹Lst. Theoretische Festkörperphysik, Universität Erlangen-Nürnberg, Erlangen, Germany — ²ETSF, Universidad del Pais Vasco, San Sebastian, Spain — ³Physics Department, King’s College, London, UK. — ⁴The Abdus Salam International Center of Theoretical Physics (ICTP) and INFM/Democritos National Simulation Center, Trieste, Italy. — ⁵Centro Mixto CSIC-UPV/EHU, San Sebastian, Spain.

Water, water clusters and ice possess the fascinating ability to bind and solvate excess electrons. On crystalline ice films on Ru(0001) a long-living excess electron state was found.¹ The electron resides in pre-existing traps at the surface and shows a continuous energy relaxation on a time scales from femtoseconds to minutes. The nature of the initial trap site and its evolution is an open question. Within the frame work of density functional theory we address prototypical trapping sites for the excess electron on (0001) surface of hexagonal ice (I_h). As the primary traps we identify admolecules, orientational defects and reconstructed orientational defects that have sufficiently low formation energy to explain the experimentally deduced abundance of trapping sites. The electron binds to the dipole moment resulting from H-O groups oriented towards the vacuum and is entirely localized in front of the surface. Its tunneling into the metal is thus sufficiently suppressed to allow for an enhancement of the screening by thermally activated reconstruction of the ice network around the trap.

[1] Bovensiepen et al J. Phys. Chem. in print.