Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 49: Oxide and Insulator Surfaces: Adsorption

O 49.6: Poster

Tuesday, March 21, 2017, 18:30–20:30, P1A

Adsorption geometry and infrared absorption of CO₂ molecules on the KCl(100) surface — •Jochen Vogt — Chemisches Institut der Otto-von-Guericke Universität Magdeburg, Germany

The system CO₂/KCl(100) is an example of a physisorption system where a moderate lattice mismatch induces a variety of phases at different coverage, both with and without long-range order. Results of diffraction experiments (LEED, HAS) and infrared spectroscopy have revealed essential adsorbate properties [1]. Simulations of the adsorbate structure on different levels of theory [1,2] are useful to complete the picture by providing suitable structure models as starting points for a LEED structure analysis, and the assignment of observed features in IR spectra. This contribution presents results of plane wave DFT calculations on the structure and infrared absorption of the saturated monolayer phase CO₂-(6√2×√2)R45^∘/KCl(100). In accordance with diffraction experiments, the relaxed geometry containing 12 tilted inequivalent molecules exhibits glide-plane symmetry, caused by a modulation of the azimuthal orientation of the molecules. The simulated IR spectrum based on a Γ-point phonon calculation is dominated by a strong red-shifted mode in the region of the CO₂ asymmetric stretch vibration, as observed in IR experiments. However, the DFT result markedly overestimates the experimentally observed exciton band width. [1] F. Traeger et al., J. Phys. Chem. A115 (2011), 6986 [2] T. Wu et al., Appl. Surf. Sci. 339 (2015), 1