developed. An implementation of CC-in-DFT for electronic excitations was presented in 2013 and applied for the calculation of solvatochromic shifts . In 2014, Höfener introduced a resolution-of-the-identity-(RI-)CC2 implementation in combination with FDE, which considerably enhanced the efficiency and thus the range of applicability of the method . It was applied to the calculation of local (uncoupled) excitation energies in a CC-in-CC framework. An extension to coupled excitations followed in 2015, where the coupling between CC2-type local excitations was treated within a coupled-cluster-singleslike approximation . Furthermore, a combination of FDE with the conductor-like screening model (COSMO) was presented in this context . For the discussion of subsequent work on analytical gradients by Höfener and co-workers, see Section 6.2.2.