Ruthenium Dioxide, a Versatile Oxidation Catalyst: First Principles Analysis
The Council for Competitiveness in Washington D.C. classifies catalysis as one of the technologies that is critical to international competitiveness of the U.S. economy. Due to the strong chemical industry in Germany this statement is equally valid for th
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Physikalisch-Chemisches Institut der U niversitat Zurich \VinterthurerstraBe 190, 8057 Zurich, Switzerland Ari. P . Sei tsonen@iki. f i Physikalisch-Chemisches Institut der Justus-Liebig-Universitat GieBen Heinrich-Buff-Ring 58, 35392 GieBen, Germany
1 Introduction The Council for Competitiveness in Washington D.C. classifies catalysis as one of the technologies that is critical to international competitiveness of the U.S. economy. Due to the strong chemical industry in Germany this statement is equally valid for the German economy. So far, efficient catalysts are designed by chemical and engineer's intuition [1]. However, the development of future and more efficient catalysts is considered to rely on atomic-scale tailored materials. To accomplish this goal a close cooperation between experimentalist, theorists as well as engineers is mandatory. It requires first of all a detailed microscopic description of catalytic reactions on the atomic scale as it is accessible by large-scale density-functional [2,3,4] calculations. During the past few years, this concept has been pursued by the Topsoe company in collaboration with the universities in Lyngby and Aarhus [5]. Very often interesting questions are posed by the experiments, although the answers are too complex to be given solely by them. This situation calls for additional information by ab-initio calculations. The other way round is also frequently encountered: Ab-initio calculations raise new questions which trigger new experiments or a different interpretation of experiments. It is just this intimate collaboration of experiment and theory that has rendered our particular project on the catalytic activity of RU02 a success story in surface chemistry of oxide surfaces [6, 7]. In this paper we will concentrate on the discussion of the theoretical results gained by large-scale DFT calculations.
2 Calculational Details In the DFT calculations we employed the generalized gradient approximation of Perdew et al. [8] for the exchange-correlation functional. We used a plane wave basis set with an energy cut-off of 60 Ry and ab-initio pseudopotentials in the fully separable form for 0, C, and Ru [9]. The Ru02(1l0) surface was modelled by five double layers of RU02 with a (2 xl) or a (1 xl) unit cell. Consecutive slabs were separated by a vacuum region of about S. Wagner et al. (eds.), High Performance Computing in Science and Engineering, Munich 2002 © Springer-Verlag Berlin Heidelberg 2003
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A.P. Seitsonen, H. Over
16k 0 and CO adsorption on Ru02(110) were modelled by placing 0 and CO on both sides of the Ru02(110) slab. In the calculations we relaxed the positions of all the 0, C, and the Ru atoms. The O-CO separation between the reacting particles defines the reaction coordinate. The transition state of each of these reaction pathways and the corresponding activation barriers were searched with a constrained minimization technique [10]. The transition state is identified when the O-CO distance reaches a value where the forces on the atoms vanish and the energ
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