To analyze this issue, we performed surface hopping simulations for free dimers using the vdW-corrected rAM1/FOMO-CIS method with the active space of four occupied and two virtual orbitals (17 Slater determinants), using the same procedure as for tetrameric systems (76 initial conditions per dimer). For dimer 3.5 Å, we obtain quantum yield Φ = 14.3 ± 4.2 %. The quantum yield is similar to that of the monomer (14.7 %), in agreement with our earlier report (employing more excitations to describe the electronic structure). For dimer 5.5 Å, we obtain a somewhat smaller quantum yield Φ = 9.3 ± 3.4 %. Thus, it appears that enlargement of the QM part (from two to four molecules) results in the reduction of the switching probability. Interestingly, this effect is observed not only for the shorter intermolecular distance (a = 3.5 Å) but also for the longer one (a = 5.5 Å).