As has already been touched upon in Section 6.2.1, this is complicated by the fact that a state-dependence of the embedding potential for a given system A in environment B arises both from a change in that environment's density ρ II , but also from a state-dependent change in the density ρ I itself through the non-additive exchangecorrelation and non-additive kinetic-energy potentials. This state-dependence of the embedding potential, in turn, leads to a non-orthogonality of the embedded wavefunctions for the states under consideration. It clearly has to be stated that non-orthogonality of the active-system wavefunctions for different electronic states in WF/DFT-embedding is not unphysical, as mentioned in various places and discussed in detail in Ref. . The latter work also highlights the conceptual differences to the case of CASSCF calculations, which may be performed in state-specific or state-averaged fashion. More importantly, it also provides some numerical data that quantify non-orthogonality effects.