Development and application of a ReaxFF reactive force field for hydrogen combustion

To investigate the reaction kinetics of hydrogen combustion at high pressure and high temperature conditions, we expanded the ReaxFF training set to include reaction energies and transition states relevant to hydrogen combustion and optimized the force field parameters against training data obtained from quantum mechanical calculations and experimental values. The optimized ReaxFF potential was used to run NVT-MD simulations for various input conditions of a H₂/O₂ mixture. We observed that the hydroperoxyl radical plays a key role in the reaction kinetics at our input conditions (T≥2750K, P > 40Mpa). The initiation reaction and the intermediate reactions are in good agreement with predictions of existing kinetic models for hydrogen combustion. Since ReaxFF is a quantum derived force field and can simulate complicated reaction pathways without any preconditioning, we believe that atomistic simulations through ReaxFF could be a useful tool in enhancing existing kinetic models for prediction of hydrogen combustion kinetics at high pressure and high temperature conditions, which otherwise is difficult to obtain through experiments.