A computational Chemistry methodology for Developing an oxygen-silica Finite rate catalytic model for hypersonic Flows: Part II

The goal of this work is to model the heterogeneous recombination of atomic oxygen on silica surfaces, which is of interest for accurately predicting the heating on vehicles traveling at hypersonic velocities. This is accomplished by creating a finite rate catalytic model, which describes recombination from an atomistic perspective with a set of elementary gas-surface reactions. In this work, we improve on our previous methodology for creating a finite rate model by including off-normal collisions in trajectory calculations and by applying detailed balance to find the reverse rates of reactions not accessible in molecular dynamics calculations. The inclusion of off-normal collisions in trajectory calculations is found to change the activation energy of the dominant reaction in the rate model, which changes the trend in recombination coefficients with temperature. We also present a separate low temperature rate model which is capable of modeling the trends seen in recombination coefficients at low temperatures. Both rate models are extremely sensitive to small changes in the activation energies of a few key reactions. To ensure the accuracy of these activation energies, new quantum chemical calculations of the specific reaction pathways observed in this work are required.