Prediction of electronic couplings for molecular charge transfer using optimally tuned range-separated hybrid functionals

Electronic coupling matrix elements are important to the theoretical description of electron transfer processes. However, they are notoriously difficult to obtain accurately from time-dependent density functional theory (TDDFT). Here, we use the HAB11 benchmark dataset of coupling matrix elements to assess whether TDDFT using optimally tuned range-separated hybrid functionals, already known to be successful for the description of charge transfer excitation energies, also allows for an improved accuracy in the prediction of coupling matrix elements. We find that this approach outperforms all previous TDDFT calculations, based on semi-local, hybrid or non-tuned range-separated hybrid functionals, with a remaining average deviation as low as ∼12%. We discuss potential sources for the remaining error.