Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 84: Density functional theory and beyond for real materials IV

O 84.1: Vortrag

Freitag, 26. März 2010, 11:15–11:30, H34

Evolution of electron traps at ice surface: aggregation of orientational defects — •Michel Bockstedte^1,2, Anja Michl¹, and Angel Rubio² — ¹Theor. Festkörperphysik, FAU Erlangen-Nürnberg, Staudtstr. 7B2, 91058 Erlangen — ²Nano-Bio spectroscopy group and ETSF, Dpto. Física de Materiales, Universidad del País Vasco, Av. Tolosa 72, E-20018 San Sebstián

Water, water clusters and ice possess the fascinating ability to solvate electrons. On crystalline ice long-living solvated electron states were observed that derive from pre-existing surface traps.¹ Theoretical models based on the bi-layer terminated I_h-(0001) relate such traps to orientational defects¹ of the otherwise ordered arrangement of water molecules at the surface.² At these traps with low formation energy, the electron attaches to the local dipole moment of OH-groups pointing out of the surface. In experiments, however, the solvated electron state was found to evolve in a thermally activated process characterized by an enhancement of its binding energy. The underlying reconstruction of the ice-trap is crucial to understand the long life time. Employing density functional theory we address the mechanism of the evolution of the initial trap. We show that an aggregation of orientational defects results in an enhanced localization of the solvated electron. The solvation-triggered aggregation yields structures with an excess energy >500 meV after the electron detachment. We discuss this mechanism in the light of an alternative evolution via the formation of voids.

[1] Bovensiepen et al J. Chem. Phys. C 113, 979 (2009).

[2] Buch et al. PNAS 105, 5969 (2008).