For the remaining off-diagonal matrix elements, an approximate TDF is needed to account for the dynamic correlation in the electronic coupling between two interacting states. Unlike KS-DFT, an approximate TDF is currently not yet available. In this study, we use an overlap-weighted average correlation energy from KS-DFT for the two individual states Ξ 𝐴𝐴 and Ξ 𝐵𝐵 to approximate the TDF correlation term: 69