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Nonadiabatic effects during the dissociative adsorption of O2 at Ag(111): A first-principles divide and conquer study

AutorGoikoetxea, Itziar ; Meyer, Jörg; Reuter, Karsten
Fecha de publicación2012
ResumenA predictive materials science modeling based on microscopic understanding requires a thorough knowledge of all underlying elementary processes at the atomic scale. The (dissociative) adsorption of individual oxygen molecules at metal surfaces is such an elementary process that is of crucial relevance for a wide range of applications involving surfaces exposed to realistic gas environments, with heterogeneous catalysis forming just one prominent example. Recent work on the dissociative adsorption of O2 at Al(111) has severely challenged the prevalent understanding of this process. Significant nonadiabatic effects, i.e. a coupled electronicnuclear motion beyond the standard BornOppenheimer approximation, have been proposed as rationalization of the experimentally observed low initial sticking probability. This behavior has been associated with the low densityofstates at the Fermilevel of the simple metal surface. If correct, this would suggest coinage metal surfaces as potential further candidates for such effects. We this motivation we perform a firstprinciples determination of the initial sticking coefficient at Ag (111). Our approach is based on a divide and conquer approach. In a first step we systematically map the underlying adiabatic potential energy surface (PES) in all six molecular degrees of freedom using density-functional theory. Symmetry adapted neural networks are then used to reliably interpolate this grid data to a continuous representation. Finally, the numerically undemanding evaluation of this representation enables a statistically reliable determination of the initial sticking coefficient through millions of molecular dynamics trajectories generated with Monte Carlo sampled initial conditions. The obtained sticking coefficient as a function of the initial kinetic energy of the impinging molecules and at different incidence angles is in good agreement with the experimentally measured curves. On the basis of these results there is thus no need to invoke significant nonadiabatic effects at this surface. However, to further investigate the role of energy dissipation into electronic degrees of freedom we perform a comparative study using two electronic friction models.
DescripciónTrabajo presentado a: "29th European Conference on Surface Science" celebrada en Edimburgo (UK) del 3 al 7 de Septiembre de 2012.
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