The db-MBE achieves this by performing the MBE not in terms of the energy, but by expanding the electron density and by applying a density-functional to evaluate a densitybased correction to the total energy of the eb-MBE. This MBE of the electron density accounts for the interactions among the polarized electron densities that only appear at higher orders in the conventional eb-MBE . Because at any given order, the eb-MBE and the db-MBE rely on the same quantum-chemical calculations for subsystems, the scaling of their computational effort with cluster size remains comparable. Therefore, accounting for many-body polarization effects already in the db-MBE(2) instead of requiring a higher-order eb-MBE reduces the overall computational effort for large systems and thus pushes the limit of the system sizes that can be treated accurately and efficiently.