Performance of optimally-tuned range-separated hybrid functionals in predicting molecular valence-electron spectra

Density functional theory with optimally-tuned range-separated hybrid (OT-RSH) functionals has been recently suggested [Phys. Rev. Lett. 109, 226405 (2012)] as a non-empirical approach to accurately predict the outer-valence electronic structure of molecules. Here, we provide a quantitative evaluation of the OT-RSH approach by examining its performance in predicting the outer-valence electron spectra of prototypical gas-phase aromatic rings. For a range of up to several eV, we find that the obtained outer-valence electronic structure agrees very well (typically within 0.1-0.2 eV) with both experimental photoemission and theoretical GW data. The sole exception found is a high-symmetry orbital that is particular to aromatic rings and occurs relatively deep inside the valence state manifold. We conclude that OT-RSH functionals offer a balanced description of differently localized electronic states, a feature we find to prevail also for the more complex terpyrimidinethiol.