A combined MD simulation and experimental investigation of the O2 formation on beta-quartz at high temperature

Using two different silica polymorphs, we have experimentaly demonstrated the impact of the surface structure in the heterogeneous recombination of atomic oxygen. Thus, the measured recombination coefficient ? of quartz is approximately three times smaller than the ? value found for ?-cristobalite at 1000 K. However, the complexity of the heterogeneous processes remains such, that Molecular Dynamics (MD) simulation became necessary to get details at the atomic level on the molecular processes underlying the experimental observations. Semi-classical MD simulations of the heterogeneous oxygen molecule formation over ?-quartz are performed according to the E-R mechanism at a surface temperature of 1000 K. The interaction dynamics takes into account the energy exchange processes between the surface atoms and the O and O2 particles in the gas phase. The O2 formation probability is calculated at different collisional energies of the incoming gas oxygen atoms, together with the probabilities of the others possible reaction channels taking place at the surface.