Figure 4.

Schematic overview of different partition schemes to deal with large systems. a) A given QM system to be computed in the gas phase. b) A QM/MM partitioning, where a QM region and an MM region interact (arrow). c) A gas‐phase exciton model partition, where several QM chromophores are computed separately and interactions (arrows) are treated in a second step. d) A QM/MM partition, where an exciton model is used for the QM region and the solvent is treated by MM, including both QM‐MM and chromophore–chromophore interactions.