during the low level steps, while for high level steps, the electronic transition are evaluated according to the FS criterion in eq. ( ) based on the high level quantities. This is not yet completely satisfactory since it does not guarantee that a transition detected with the LZ probabilities during a low level step would have also been detected by the FS criterion calculated with the high level functional. To further improve on that issue, we suggest that if a transition is detected at the low level (using LZ theory), a high level calculation is triggered to confirm the transition using Tully's FS criterion. This strategy is described in algorithm 3 and tested in the remaining sections.