Accurate molecular geometries in complex excited-state potential energy surfaces with optimally-tuned range-separated hybrids

The computational investigation of the excited-state (ES) potential energy surfaces (PES) involved in important photocatalytic reactions (e.g., water splitting) can shed light on reaction mechanisms and pathways. These ES PES can be obtained using time-dependent density functional theory (TD-DFT) or high-level wave-function methods. Calculations based on TD-DFT are computationally very efficient but often do not reach the accuracy of computationally more expensive wave-function methods[1]. One promising approach to reduce this gap in accuracy is the recently developed class of optimally-tuned range-separated hybrid (OT-RSH) functionals[2].
In this work, we assess the precision of excited-state geometries obtained with TD-DFT and OT-RSH for a selection of organic molecules with varying complexity of their ES PES. We focus on structural parameters of the lowest-excited singlet states and compare them to high accuracy wave-function data from literature. Our results show that OT-RSH maintains the accuracy of conventional functionals for small molecules and that they improve the description of more complex ES PESs involving charge-transfer states.

[1] C. Azarias, J. Phys. Chem. A, 121, 32, 6122 (2017)
[2] L. Kronik et al., J. Chem. Theory Comput., 8, 5, 1515 (2012)