Subsystem embedding thus changes the polarizability. As the sum over occupied orbitals is limited to the active occupied orbitals, contributions to the screening from transitions that start from "originally" occupied orbitals of the embedding region are missing. This results in changes of the response even if the ϕ(r) and energies ε were unchanged. The lack of screening contributions from the now inactive region, generally translates into weaker contributions of Σ c to the quasiparticle energies (in absolute values) in the DFT-embedded GW calculation compared to the full GW case. Even in weakly interacting, non-bonded molecular structures, for instance, where the orbitals themselves are only minimally affected by the embedding, one can expect to find the occupied (virtual) quasiparticle energies below (above) the ones from the full calculations. That means, in turn, that the HOMO-LUMO gap in subsystem-GW is also larger than the respective gap in full-system GW .