Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 58: Surface chemical reactions II
O 58.8: Vortrag
Mittwoch, 24. März 2010, 16:45–17:00, H42
First-principles assessment of UBI-QEP derived rate constants for chemical kinetics — •Matteo Maestri1,2 and Karsten Reuter1,3 — 1Fritz-Haber-Institut Berlin, Germany — 2Politecnico di Milano, Italy — 3TU München, Germany
An accurate description of the elementary steps involved in a catalytic process is the basis for a reliable microkinetic modeling of the surface chemistry. Though desirable, a first-principles calculation of the reaction parameters is presently unfeasible but for models involving a small number of reactions. For complex catalytic systems, semi-empirical approaches, such as the UBI-QEP method [1], are therefore often employed to estimate reaction barriers and coverage effects. While computationally less demanding, the accuracy of UBI-QEP is uncertain and one has to question whether the corresponding energetics are mere artifacts of the employed effective modeling. At this scope and using the water-gas shift reacting system on Rh(111) as a showcase, we perform a density-functional theory based assessment of the UBI-QEP derived rate constants for specific classes of reactions (namely, dissociation/recombination and disproportionation). This comprises in particular the explicit coverage dependence of the reaction barriers predicted within the UBI-QEP framework. In doing so we aim at an increased awareness of the limitations of UBI-QEP methodology and the demonstration of possible strategies to overcome them. [1] E. Shustorovich and H. Sellers, Surface Science Reports, 31 (1998) 5.