Berlin 2001 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 16: Poster: Dynamics of Molecular Systems, Polymer Dynamics, Glass Transition, Crystallization, Electronic Properties of Polymers

CPP 16.5: Poster

Monday, April 2, 2001, 12:30–15:00, AT1

On the Nature of the Electronic Control of Elastic Properties of Corundum Ruthenium and Rhodium Sesquioxides — •M.E. Grillo, M.V. Ganduglia-Pirovano, and M. Scheffler — Fritz-Haber Institut, Faradayweg 4-6, D-14195 Berlin

Commercial needs of improving durability and performance of supported Ru and Rh catalysts [1] drives the interest in investigating the structural changes occurring during deactivation. The present work investigates, on one hand, the electronic factors controlling the chemical equilibrium between different ruthenium oxide phases, namely, RuO₂-rutile and Ru₂O₃-corundum. In fact, both the athermal total pressure- and oxygen partial pressure-dependence of the chemical equilibrium of corundum to rutile ruthenium oxide decomposition will be presented, supported by density functional calculations. The equilibrium structures, binding energies, and high pressure behavior of all oxide phases were determined, fitting the calculated total energies as a function of volume to the Murnaghan equation of state. Based on the analysis of the density of states and valence charge densities, the calculated high bulk modulus for Ru₂O₃ is explained by the strong Ru-O covalent bonding, as compared to the significant ionic-character of the Rh-O bonding. [1]C. Wong and R.W. McCabe, J. Catal. 119, (1989) 47.