Molecular
dynamics (MD) simulations provide an important link between
theories and experiments. While ab initio methods
can be prohibitively costly, the ReaxFF force field has facilitated in silico studies of chemical reactivity in complex, condensed-phase
systems. However, the relatively poor energy conservation in ReaxFF
MD has either limited the applicability to short time scales, in cases
where energy propagation is important, or has required a continuous
coupling of the system to a heat bath. In this study, we reveal the
root cause of the unsatisfactory energy conservation, and offer a
straightforward solution. The new scheme results in orders of magnitude
improvement in energy conservation, numerical stability, and accuracy
of ReaxFF force fields, compared to the previous state-of-the-art,
at no additional cost. We anticipate that these improvements will
open new avenues of research for more accurate reactive simulations
in complex systems on long time scales.