Assessing challenging intra‐ and inter‐molecular charge‐transfer excitations energies with double‐hybrid density functionals

We investigate the performance of a set of recently introduced range‐separated double‐hybrid functionals, namely ωB2‐PLYP, ωB2GP‐PLYP, RSX‐0DH, and RSX‐QIDH models for hard‐to‐calculate excitation energies. We compare with the parent (B2‐PLYP, B2GP‐PLYP, PBE0‐DH, and PBE‐QIDH) and other (DSD‐PBEP86) double‐hybrid models as well as with some of the most widely employed hybrid functionals (B3LYP, PBE0, M06‐2X, and ωB97X). For this purpose, we select a number of medium‐sized intra‐ and inter‐molecular charge‐transfer excitations, which are known to be challenging to calculate using time‐dependent density‐functional theory (TD‐DFT) and for which accurate reference values are available. We assess whether the high accuracy shown by the newest double‐hybrid models is also confirmed for those cases too. We find that asymptotically corrected double‐hybrid models yield a superior performance, especially for the inter‐molecular charge‐transfer excitation energies, as compared to standard double‐hybrid models. Overall, the PBE‐QIDH and its corresponding range‐separated RSX‐QIDH functional are recommended for general‐purpose TD‐DFT applications, depending on whether long‐range effects are expected to play a significant role.