Coupled-Cluster Frozen-Density Embedding Using Resolution of the Identity Methods

Frozen-density embedding (FDE) is combined with resolution of the identity (RI) Hartree-Fock and a RI-variant of a second-order approximate coupled-cluster singles and doubles (RI-CC2) to determine solvatochromic shifts for the lowest excitation energy of acetone and pyridazine, respectively, each solvated in different environments with total system sizes of about 2.5 nm diameter. The combination of FDE and RI-CC2 increases efficiency and enables the calculation of numerous snapshots with 100 to 300 molecules, also allowing for larger basis sets as well as diffuse functions needed for an accurate treatment of properties. The maximum errors in the solvatochromic shifts amount up to 0.2 eV, which are similar to other approximated studies in the literature. (C) 2014 Wiley Periodicals, Inc.