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Interaction of molecular oxygen (O2) with carbon-based surfaces at high temperatures is highly relevant in the fields of production of fuels from coal and degradation of polymeric material in space-craft reentry vehicles in the low-earth orbits (LEO). While the representative reaction is deceptively simple, the underlying mechanism is extremely complex, given the number of factors involved in the reaction. Herein, using direct dynamics simulations with VENUS-MOPAC software, the mechanism of dissociative chemisorption of O2 on defect-free and defective graphene surfaces is studied. For the first time, the necessary and sufficient conditions for O2 dissociative chemisorption on graphene surfaces are established using direct dynamics simulations. Further, the applicability and appropriateness of semi-empirical methods like PM7 as implemented in MOPAC for such problems involving various electronic states, morphology and temperature dependence of direct dynamics simulations of O2 collisions with defect-free and defective graphene, successes and limitations of these simulations, comparison with experiments and alternative methods for accurate simulations of these types of reactions will be discussed. |