Regensburg 2016 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 14: Surface Chemical Dynamics
O 14.9: Vortrag
Montag, 7. März 2016, 17:15–17:30, S053
Exciting phonons: When molecules meet surfaces — •Vanessa Jane Bukas and Karsten Reuter — TU München, Germany
Exothermic surface chemical reactions may easily release several electron volts of energy. This challenges first-principles based dynamical simulations to account for adequate energy dissipation channels. Focusing on phononic dissipation, a novel embedding scheme for metallic substrates (QM/Me [1]) allows for energy to be dissipated out of a quantum-mechanically described reaction zone and into a computationally undemanding, yet reliably described, extended bath. In the application to oxygen dissociation over Pd(100) this approach predicted “hot” O adatoms traveling ballistically over several lattice constants as a consequence of non-immediate energy transfer to the surface [1].
Despite being similarly exothermic, a much shorter transient mobility was measured for the O2/Pd(111) reaction [2]. We reconcile this apparent intricacy by quantitatively analyzing the underlying phonon excitations directly from QM/Me trajectories. This identifies certain groups of localized surface modes as the dominant dissipation channels, while comparing the Pd(100) and Pd(111) systems offers important trend understanding into the influence of surface symmetry. The thus obtained first-principles perspective on non-equilibrium adsorbate-phonon dynamics questions prevalent assumptions about energy sinks made in commonly used model Hamiltonians.
[1] J. Meyer and K. Reuter, Angew. Chem. Int. Ed. 53, 4721 (2014).
[2] M.K. Rose et al., Surf. Sci. 561, 69 (2004).