A Finite-Rate Gas-Surface Interaction Model Informed by Fundamental Computational Chemistry Simulations
Final rept. 1 Apr 2012-31 Mar 2013
MINNESOTA UNIV MINNEAPOLIS
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A finite-rate gas-surface model for use as a CFD boundary condition specific to oxygen-silica reactions was formulated using computational chemistry calculations. A new interatomic potential was developed and made publicly available specifically for oxygen-silica gas-surface reactions ReaxFF-SiO-GSI using a large database of density functional theory single point energies. Computational chemistry calculations predicted a number of surface defects on realistic silica surfaces in agreement with experimental data which participate in the surface recombination of oxygen. The dominant reaction pathways occurring on these defects were studied by MD simulations of oxygen impacts. Steric factors and activation energies were computed for each reaction and the resulting model was formulated to satisfy detailed balance. The dominant mechanisms were found to not be activated processes no energy barriers, resulting in little temperature dependence on recombination efficiencies. Product molecules resulting from a single collision-based reaction were found to not thermally accommodate to the surface, rather they leave in excited vibrational levels. The new finite-rate model and thermal accommodation results can be directly used in CFD calculations.
- Physical Chemistry