1 Recombination and chemical energy accommodation coefficients from chemical dynamics simulations: O/O2 mixtures reacting over a b-cristobalite (001) surface a Víctor Morón, a,c Pablo Gamallo, b,c Ludovic Martin-Gondre, d Cédric Crespos, d Pascal Larregaray and a Ramón Sayós a Departament de Química Física and Institut de Química Teòrica i Computacional, Univ. Barcelona, C. Martí i Franquès 1, 08028 Barcelona, Spain b Centro de Física de Materiales (CFM), Centro Mixto CSIC-UPV/EHU, P. Manuel de Lardizabal 5, 20018 San Sebastián, Spain c Donostia International Physics Center (DIPC), P. Manuel de Lardizabal 4, 20018 San Sebastián, Spain d Institut des Sciences Moleculaires, UMR 5255 CNRS-Université Bordeaux I, 33405 Talence Cedex, France. Abstract: A microkinetic model is developed to study the reactivity of an O/O2 gas mixture over a b-cristobalite (001) surface. The thermal rate constants for the relevant elementary processes are either inferred from quasiclassical trajectory calculations or using some statistical approaches, resting on a recently developed interpolated multidimensional potential energy surface based on density functional theory. The kinetic model predicts a large molecular coverage at temperatures lower than 1000 K, in contrary to a large atomic coverage at higher temperatures. The computed atomic oxygen recombination coefficient, mainly involving atomic adsorption and Eley-Rideal recombination, is small and increases with temperature in the 700-1700 K range (0.01 < gO < 0.02) in good agreement with experiments. In the same temperature range, the estimated chemical energy accommodation coefficient, the main contribution to which is the atomic adsorption process is almost constant and differs from unity (0.75 < bO < 0.80). Keywords: Adsorption, sticking, surface reactions, b-cristobalite, atomic oxygen, molecular oxygen, microkinetic model, density functional theory, quasiclassical trajectories, atomic recombination coefficient, chemical energy accommodation coefficient Tables: 1 Figures: 8 Proofs to: Prof. R. Sayós * Author for correspondence: e-mail: r.sayos@ub.edu (version: 05/07/2011)