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O: Fachverband Oberflächenphysik

O 66: Oxide Surfaces II

O 66.2: Vortrag

Donnerstag, 14. März 2013, 10:45–11:00, H42

Carboxylic acid on all stable TiO₂ rutile surfaces: Comparison of DFT and DFTB potentials — •Wolfgang Heckel, Beatrix Elsner, and Stefan Müller — Hamburg University of Technology, Institute of Advanced Ceramics, Denickestr. 15, D-21073 Hamburg

In order to control the mechanical properties of hybrid materials, the detailed knowledge of the interfaces, the atomic structure and stability is crucial. Both methods, density functional theory (DFT) and density functional based tight binding (DFTB) allow for the investigation of the local electronic structure and the determination of desired observables like binding energy, while growing further towards about 5-10 times larger model systems with the latter.

As a prototype adsorbate we tested acetic acid on TiO₂ (110), (011) and (100) surfaces for two DFT exchange-correlation functionals (PBE and PBEsol) and for DFTB being able to estimate the accuracy of results for arbitrary adsorbates in the future.

We put the focus on the ability of the methods to describe correctly the role of the carboxylic hydrogen ion, which dissociates during adsorption and forms an OH species stabilizing the adsorption, as shown in experiments (e. g. [1]). All methods applied prefer the dissociated adsorption mode to the molecular mode, however the results differ about prefering acetic acid or acetate.

Supported by DFG, SFB 986, project A4.

[1] Sayago et al., J. Phys. Chem. B 108, 14316 (2004)