Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 100: Metal Substrates: Adsorption and Reactivity

O 100.7: Vortrag

Freitag, 20. März 2015, 12:00–12:15, MA 043

Correlation between adsorption and strain: a first-principles study of the H/Ir(111) system — •Anja Michl and Stefan Müller — Hamburg University of Technology, Institute of Advanced Ceramics, Denickestr. 15, D-21073 Hamburg

The interaction of hydrogen with Iridium surfaces is relevant for a wide range of catalytic reactions. Straining the catalysts surface has an impact on adsorption energies and energy barriers and thus can be used to tune the catalytic activity.

We use density functional theory (DFT) to study the energetics of hydrogen adsorption on Ir(111). Vibrational frequencies are determined to account for zero-point energy corrections. The most favorable adsorption configurations are identified by using the DFT data to construct a cluster-expansion Hamiltonian, which enables an exhaustive scan of the configuration space. We find that top site adsorption is preferred over the whole coverage range from 0 to 1 ML. At low coverage the distance between adsorbed hydrogen atoms is maximized, while at higher coverage ground states exhibit hydrogen covered stripes of varying width. However, the ordering tendencies of the system are not very pronounced, with energy differences less than 30 meV per 1×1 surface site. Biaxial strain in the surface plane is applied to energetically favorable configurations in order to reveal strain-induced changes in the energetic hierarchy and to determine the coupling strength between adsorption energies and strain.