In addition, to better describe noncovalent interactions, we have added van der Waals (vdW) interaction terms, described with the Lennard-Jones potential, between atoms of different monomers (3456 pairwise potentials in total, for the QM part). The atomic vdW parameters were taken from the OPLS-AA force field. The parameters for atom pairs were calculated taking a geometric mean of the atomic parameters. The used atomic parameters are σ C = 3.55 Å, σ H = 2.42 Å, σ N = 3.25 Å, ϵ C = 0.07 kcal/mol, ϵ H = 0.03 kcal/mol, ϵ N = 0.17 kcal/mol. The MM part of the SAM models interacts with the QM part by the same vdW interaction and the MM molecules were kept fixed during molecular dynamics (MD) simulations. In addition, for the QM tetramer, the C and H atoms closest to an (imaginary) surface (two per monomer) were kept fixed, as in our previous works. Ground-state Langevin MD simulations (on the S 0 rAM1/FOMO-CIS potential energy surface (PES)) were performed to equilibrate the studied systems at T = 300 K. The dynamics were run for 20 ps with a time step of 0.2 fs. For each system, the geometries and velocities were selected from the ground-state trajectories every 200 fs, starting at 5 ps, which results in 76 initial conditions (for surface hopping dynamics simulations) per system. These selected, initial geometries are shown in Figure .