The initial conditions for the trajectory-based simulations were obtained by sampling N tr = 1000 positions and momenta from the harmonic Wigner distribution obtained from the vibrational ground state in the electronic ground state, centered at q = 0 with zero average initial momentum. In all cases, the dynamics was initiated by supposing an instantaneous excitation in the FC region, thus promoting the system from the electronic ground state to the bright state, which is S 2 for DMABN and S 1 for fulvene. As mentioned in the Introduction, the dynamics was simulated in full dimensionality, thus using N modes = 57 for DMABN and N modes = 30 for fulvene. Even though the actual dynamics in DMABN takes place between S 1 and S 2 , the LVC model includes three electronic states, and all three were considered in our simulations (but the ground state is not populated in the course of the simulated dynamics). The time step was chosen to be dt = 0.0024 fs (0.1 a.u.), and all trajectories were propagated for 100 fs. Some reference data were reported in Ref. [73] employing the multi-layer version of multi-configuration timedependent Hartree (MCTDH) method . MCTDH calculations were performed in the diabatic basis and, consequently, the populations of the electronic diabatic states are provided for comparison. Therefore, since QuantumModelLib provides the matrix that diagonalizes the electronic Hamiltonian (12) as function of q, we used it to determine the diabatic populations from the vectors of electronic adiabatic coefficients C l (q, t) that are calculated using G-CTMQC. In doing so, we observed that the initialization of DMABN dynamics using the trajectories in S 2 does not reproduce the initialization with MCTDH in the diabatic state 2. This is because in the FC region, the adiabatic state S 2 has a mixed diabatic character. In order to provide direct comparison with MCTDH results for DMABN, we also performed additional simulations with MTE and CTMQC by initializing the electronic state in a superposition of S 1 (10%) and S 2 (90%) so as to fully populate the diabatic state 2 at time 0, as in MCTDH, and provide a direct comparison between the quantum and the quantum-classical dynamics. These additional calculations are not necessary for fulvene, since in the FC region the adiabatic state S 1 does not show a mixed diabatic character.