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O: Fachverband Oberflächenphysik

O 49: Metal Substrates: Structure, Adsorption and Growth

O 49.11: Poster

Dienstag, 8. März 2016, 18:15–20:30, Poster E

A first-principles study of chemo-mechanical coupling for hydrogen on Ir(111) — •Anja Michl, Gregor Feldbauer, and Stefan Müller — Hamburg University of Technology, Institute of Advanced Ceramics

Mechanical strain has an impact on the energetics of adsorption and transition states of chemical reactions on surfaces. Therefore, it is possible to tune the reactivity by changing the lattice parameter of the catalyst's surface. Since the interaction of hydrogen with iridium surfaces is relevant for a wide range of catalytic reactions, H/Ir(111) was chosen as a model system.

We use density functional theory (DFT) in conjunction with the cluster-expansion method to investigate the energetics of hydrogen adsorption on Ir(111) and its response to strain. DFT data for various configurations with different H coverages and adsorption sites serve as input for a cluster expansion. This approach allows for an exhaustive scan of the configuration space and thus to identify the most favorable structures as a function of coverage. While top-site adsorption is preferred, the system exhibits only a weak tendency for ordering. Moreover, biaxial strain in the surface plane is applied to different configurations to elucidate the correlation between adsorption energies and mechanical strain. In order to gain further insight into the underlying mechanisms, we also analyze the adsorbate induced work function change and its relation to charge transfer.