The total number of time steps for each O impact was 3000 for 1eV energy and 4000 for 10 and 30 eV impact energies. Each O impact caused a collisional cascade on the picosecond time scale, and the surface processes were allowed to evolve without forced exchange of energy with the environment. After incident O atom thermalization due to the collisional cascade, the entire system underwent a cooling to 300 K by applying the Langevin thermostat for 0.5 ps, which dissipated any excess heat resulting from an impact and emulated the natural or forced cooling process occurring over much longer timescales. The cooling step was imperative due to the disparity in time scales between molecular dynamics simulations (ranging from femtoseconds to nanoseconds) and real experiments, where the irradiation flux is usually many orders of magnitude smaller, allowing cooling to a desired average temperature of the slab. The simulation process produced the oxygen irradiation fluence of 8.5×10 20 atoms/m 2 after 4500 atom impacts. The deposition flux was 2.83×10 32 atoms/m 2 sec for the 1 eV O impact energy case and 2.1×10 32 atoms/m 2 sec for the 10 and 30 eV incident energy cases.