where E I are the energies of the monomer fragments, ∆E IJ are the interaction energies of dimers, ∆E IJK are the interaction energies of trimer, and so on. This approach can be combined with sDFT/FDE in two different ways . On the one hand, FDE can be used to include a frozen environment of the remaining fragments in the calculation of the monomer, dimer, trimer etc. energies. This accelerates the convergence of the manybody expansion (for a study in the context of FDE, see Ref. ), but does not improve substantially compared to conventionally point-charge embedding.