In the PE-DFT framework, the site energy is the excitation energy related to a single chromophore. â † m,p is a creation operator that creates the pth excited state on molecule m, and âm,p is the corresponding annihilation operator. The second term in eq 7 describes the transfer of the excitation between molecule m and n. J pq mn is the exciton coupling between molecule m in the pth excited state and molecule n in the qth excited state, which, when calculated in presence of a polarizable environment, has two overall contributions J pq mn = J pq mn (0) + J pq mn .