Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 29: Poster session II (Nanostructures, Magnetism, Particles and clusters, Scanning probe techniques, Time-resolved spectroscopy, Structure and dynamics, Semiconductor surfaces and interfaces, Oxides and insulators, Solid-liquid interfaces)
O 29.61: Poster
Mittwoch, 29. März 2006, 14:30–17:30, P2
Experimental and theoretical studies of the structure and dynamics of the CaF2(111) surface — •A. Gotte1, M. Baudin1, K. Hermansson1, A. Cabello2, J. Vogt2, and H. Weiss2 — 1Department of Materials Chemistry, The Ångström Laboratory, Box 538, 752 21 Uppsala, Sweden — 2Chemisches Institut der Universität Magdeburg, Universitätsplatz 2, 39106 Magdeburg, Germany
The structure and dynamics of the CaF2(111) surface was investigated by means of low-energy electron diffraction (LEED) and molecular dynamics (MD) simulations at 300 K. LEED beam intensities were recorded as a function of electron energy and were analyzed with the tensor LEED approach. Positions as well as mean square amplitudes (MSA) of the ions in the first layers were fitted to the experimental I(E) curves. The MD simulations were performed using a 2-dimensional slab representation of the surface. Short-range interactions were described by a Buckingham potential and long-range interactions were calculated using a 2-D Ewald summation technique. Ionic polarizations were included by the shell-model. All parameters of the force field were fitted to the experimental bulk structure and elastic and dielectric data. According to experiment and theory the structure of the CaF2(111) surface is close to the bulk-terminated geometry with only small vertical displacements of the topmost ions. Moreover it is found that the MSAs of the anions are larger than those of the cations. Enhanced vibrational amplitudes of the ions in the surface layers are supported by both studies, although with different values of the respective MSAs.