Regensburg 2004 – scientific programme
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O: Oberflächenphysik
O 26: Adsorption an Oberflächen II
O 26.3: Talk
Tuesday, March 9, 2004, 16:15–16:30, H45
Non-adiabatic spin effects in O2 dissociation at Al(111) — •Jörg Behler1, Sönke Lorenz1, Bernard Delley2, Karsten Reuter1, and Matthias Scheffler1 — 1Fritz-Haber-Institut, Faradayweg 4-6, D-14195 Berlin — 2Paul Scherrer Institut, CH-5232 Villigen PSI
The experimentally well established low initial sticking coefficient of thermal oxygen molecules impinging on an Al(111) surface is still lacking a physical explanation. The calculation of the six-dimensional potential energy surface using density functional theory (DFT) followed by extensive molecular dynamics (MD) simulations results in a far too high sticking probability due to the absence of energy barriers in this adiabatic description. By including a constrained DFT method we extend this standard approach to describe the spin triplet state of the oxygen molecule and the singlet state of the metal surface. This is a generalization of the fixed spin moment approach, and it enables us to investigate the effect of non-adiabatic processes in the dissociative adsorption. For the total energy surface of the spin triplet O2 we find energy barriers up to 0.5 eV for most molecular orientations agreeing well with the experimental data. MD simulations on this surface yield a significantly lower sticking probability than obtained in the adiabatic case.