Dielectric-Screened Functionals for Cis–Trans Excitation Energies of Solvated Azobenzene Derivatives: Screening Trends in Comparison with Experiment and Published GW/BSE Calculations

We present a mean-field approach that combines density functional theory with a polarizable continuum model (PCM) to account for environmental dielectric screening, providing an efficient mean-field alternative to higher-cost wavefunction- or many-body-based approaches.

The framework employs dielectric-screened range-separated hybrid (SRSH) functionals within PCM to obtain excited states of solvated azobenzene derivatives, a prototypical molecular photoswitch. SRSH–PCM excitation energies better reproduce experiment when the larger static dielectric constant, which also accounts for nuclear polarization, is used to define long-range screening. Using the smaller optical dielectric constant, which represents purely electronic polarization, SRSH–PCM energies align better with previously reported high-quality GW–Bethe–Salpeter equation (GW/BSE) energies [Kshirsagar et al., JCTC 2020].