Additionally, FEM calculations have been done for each system, using the same level of theory and the same sets of site states as in ECI+FDA. As discussed above, ECIS+FDA is conceptually very similar to the FEM, with the only difference being that ECIS+FDA does not neglect the interfragment interaction energy on the diagonal, and GS-LE and the same-site LE-LE couplings. Nevertheless, as we will show below, the performance of ECIS+FDA and the FEM is substantially different.