The mean-field character of the Ehrenfest approach is not able, by construction, to capture with trajectories the dynamics just described, characterized by a final density that proceeds along diverging paths. This is very clearly represented by the circles in the upper left panel of Fig. , that show the positions of the Ehrenfest trajectories at the same time snapshots of the density, along with the potential energy felt by those trajectories, whose gradient is used to compute the force. The absence of the splitting in the distribution of trajectories yields wrong nuclear dynamics, and, consequently, it is not surprising that the population of the excited state (lower left panel of Fig. ) at the end of the simulated dynamics is not correctly reproduced by Ehrenfest. The surface-hopping approach cures the mean-field problem of Ehrenfest. Specifically, the trajectories follow at all times either one or the other potential energy, that is why the circles on the right panel of Fig. are distributed always either on the ground-state or on the excitedstate energy curve. Surface-hopping trajectories correctly reproduce the splitting of the nuclear density since a hopping algorithm allows them to change instantaneously the potential that drives their dynamics (so-called, active state), with high probability in the region of strong nonadiabaticity. Nonetheless, the disconnect between the potential (or the force) that drives the dynamics of the trajectories and the evolution of the electronic coefficients (similarly to the Ċα l (t) above) is often source of disagreement between the two ways of estimating the electronic populations: one way is to count the fraction of trajectories in each state, while the other is via the coefficients. This problem, related to the concepts of internal consistency and of overcoherence of the algorithm, clearly appears at the final times of the simulated dynamics (lower right panel of Fig. ), where the purple-dashed and blue-continuous curves diverge.