This will be computationally demanding for large aggregates and using the so far-described DFT-based methods. To cope with this situation approximate DFT-based tight-binding has been suggested for efficient parametrization of the FEH and applied to calculate spectral densities for a molecular crystal. Although most applications focus on the energetically lowest valence excitations, core excitations as well as highly excited valence states of molecular dimers have also been considered. In Ref. 18 a hemin dimer was studied to identify spectral signatures of dimerization.