Regensburg 2007 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 51: Metal Substrates: Adsorption III
O 51.5: Vortrag
Donnerstag, 29. März 2007, 12:15–12:30, H39
Hindered Spin-Transitions in the Dissociative Adsorption of O2 on Al(111) — •Christian Carbogno1, Jörg Behler2, Axel Groß1, and Karsten Reuter3 — 1Inst. of Theoretical Chemistry, University of Ulm, Germany — 2Dept. of Chemistry and Applied Biosciences, ETH Zürich, Switzerland — 3Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany
The low sticking probability for thermal O2 molecules at Al(111) has recently been related to spin selection rules, which hinder a spin transition from the initial O2 gas-phase triplet state to the singlet state of the adsorbed O atoms [1]. A constrained density-functional theory (DFT) approach was employed to compute the potential energy surfaces (PESs) of O2 in different spin-configurations, and the lowered sticking probability was calculated when restricting the O2 molecule to motion on the spin-triplet PES only. Here, we extend these studies by considering the dissociation dynamics on multiple spin PESs, allowing transitions between them within the quantum-classical fewest-switch algorithm as recently implemented [2], and calculating the non-adiabatic coupling between the PESs with various quantum chemical methods. The established framework enables us to study the adsorption process in detail, both as a function of the incident kinetic energy and incidence angle. Obtaining good agreement with experiment, we critically discuss the effects of the approximate non-adiabatic couplings and the uncertainties underlying the DFT PESs.
[1] J. Behler et al., Phys. Rev. Lett. 94, 036104 (2005).
[2] C. Bach et al., Israel J. Chem. 45, 46 (2005).