Dresden 2003 – wissenschaftliches Programm
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O: Oberflächenphysik
O 9: Adsorption an Oberfl
ächen I
O 9.8: Vortrag
Montag, 24. März 2003, 16:45–17:00, FOE/ANOR
Non-adiabatic spin effects in O2 dissociation on 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 physical origin of the experimentally well established low sticking coefficient for thermal oxygen molecules impinging on an Al(111) surface is still not understood. By calculating the adiabatic six-dimensional potential energy surface using density functional theory (DFT) and subsequent molecular dynamics this sticking behaviour cannot be accounted for. Therefore we extend this standard approach by including a constrained DFT method to describe the spin triplet state of the oxygen molecule accurately while keeping the metal surface in a singlet state. This approach, though similar in spirit, is an improvement over standard fixed spin moment calculations and allows to investigate non-adiabatic effects. Due to the large adsorption energy of oxygen atoms and to the small molecular weight of the Al atoms we additionally investigate the motion of the surface atoms during the adsorption process by ab initio molecular dynamics. This motion is expected to have a strong influence on the adsorption mechanism.