Electronic Band Shapes Calculated with Optimally Tuned Range-Separated Hybrid Functionals.

Abstract

Using a set of 20 organic molecules, we assess the accuracy of both the absorption and emission band shapes obtained by two optimally tuned range-separated hybrid functionals possessing 0% (LC-PBE*) and 25% (LC-PBE0*) of short-range exact exchange as well as by four other hybrid functionals including or not dispersion and long-range corrections (APF-D, PBE0-1/3, SOGGA11-X, and ωB97X-D). The band topologies are compared to experimental data and to previous time-dependent density functional theory calculations. It turns out that both optimally tuned functionals vastly improve the vibronic band shapes obtained with the non-tuned LC-PBE approach but, statistically, do not yield more accurate topologies than standard hybrid functionals. In other words, optimal tuning allows to obtain more accurate excited-state energies without degrading the description of band shapes. In addition, the LC-PBE0* 0-0 energies have been determined for a set of 40 compounds, and it is shown that the results are, on average, less accurate than those obtained by LC-PBE* for the same panel of molecules. The correlation between the optimal range-separation parameters determined for LC-PBE* and LC-PBE0* is discussed as well.