Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

O: Fachverband Oberflächenphysik

O 69: Focussed Session: Towards a Quantitative Understanding of Complex Adsorption Structures: Surface Science goes Organic II

O 69.3: Vortrag

Donnerstag, 3. April 2014, 11:15–11:30, HSZ 01

Simulating X-ray absorption spectra of large organic adsorbates with DFT: possible pitfalls on the example of free-base porphine on Ag(111) and Cu(111) — •Katharina Diller, Reinhard J. Maurer, and Karsten Reuter — Technische Universität München, Germany

Near-edge X-ray Absorption Fine-Structure (NEXAFS) spectroscopy is widely used in Surface Science for the characterisation of adsorbate-substrate systems. Especially for large organic molecules, however, the spectral features consist of a set of overlapping peaks and cannot be disentangled easily. For many systems an independent first-principles simulation of the respective spectra is therefore indispensable for the analysis of the experimental data. Particularly for stronger chemisorbed adsorbates the (often applied) approximation to restrict the calculations to the isolated gas-phase molecule is bound to fail. On the other hand, explicit consideration of in particular extended metal surfaces faces multiple challenges that mostly arise from the need to keep the calculations computationally tractable. Using the adsorption of free-base porphine on Ag(111) and Cu(111) as example we conduct density functional theory (DFT) simulations using both all-electron (FHI-aims) and pseudopotential (CASTEP) based implementations to investigate the efficiency and reliability of prevalent approaches to achieve the actual core-excitation, to ensure the localization of the core-hole, and to properly describe all final states of interest.