Geometry Optimization with the Optimally Tuned Range-Separated Hybrid Functional

The state-of-the-art DFT is, as it turns out, too accurate for gas-phase calculations to be relevant to materials research.  Dielectric effects can be readily accounted for within the optimally tuned range-separated hybrid (OT-RSH) functional framework thanks to recent efforts to incorporate the continuum solvation model (see highlight).  Still, calculating the geometry with the same level of accuracy hasn’t been straightforward due to the so-called size consistency error. In their most recent work, Han and Kim at Dankook University in Korea have demonstrated that geometry optimization, when combined with dielectric screening, can effectively remove the size consistency error.  With geometry optimization at their disposal with the same ease enjoyed by the standard functionals, they applied OT-RSH to a conformationally bistable organic molecule to understand how a changing dielectric environment affects the key photophysical parameters of thermally activated delayed fluorescence (TADF) and persistent room-temperature phosphorescence (PRTP).

tuning RSH with solvent during geometry optimization

You may also want to check out our TADF optimization tutorial!

H. Han and E.-G. Kim, “Dielectric Effects on Charge-Transfer and Local Excited States in Organic Persistent Room-Temperature Phosphorescence,” Chemistry of Materials 31, 6925–6935 (2019)

Key concepts