While it may seem trivial to equilibrate the crystal structure at room temperature, we want to detail this here because we have found that it is a crucial step. This is true in particular when we want to simulate with ReaxFF structures that originate from different levels of theory or come from experiments, therefore with different structural characteristics -for which features of the original model should be retained. We do this by imposing constraints on the energy, temperature and volume of the system, and successively releasing them.