Dresden 2014 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 82: Metal Substrates II
O 82.5: Vortrag
Donnerstag, 3. April 2014, 17:00–17:15, WIL A317
Ground-state structures for oxygen adsorption on Ir(100)-(1×1) investigated via the cluster-expansion method — •Anja Michl1,2, Pascal Ferstl3, Lutz Hammer3, M. Alexander Schneider3, and Stefan Müller2 — 1Institute of Materials Research, Materials Mechanics, Helmholtz-Zentrum Geesthacht, Germany — 2Institute of Advanced Ceramics, Hamburg University of Technology, Germany — 3LS f. Festkörperphysik, Universität Erlangen-Nürnberg, Germany
The interaction of oxygen with transition metal surfaces is of fundamental importance for a variety of processes in heterogeneous catalysis. In the case of iridium, oxygen exposure lifts the (5×1)-hex reconstruction of the (100) surface leading to a (1×1) structure.
We performed an exhaustive ground-state search for the O/Ir(100)-(1×1) system by using the cluster-expansion formalism in conjunction with first-principles calculations. Our study reveals (n×1)-mO superstructures as the dominant structural motif of energetically favorable structures, where the periodicity n and the number of oxygen atoms in the unit cell m vary with the coverage. Bridge site occupation is preferred and the most pronounced ground state ist the well-known (2×1)-br superstructure. At low coverage, structures formed by an alternation of (2×1)-br stripes and a shifted row reconstruction have lower formation energies than the corresponding structures on a merely (1×1) ordered substrate. Our findings are in agreement with experimental data obtained by STM and LEED.