Fast and Reliable Excited State Hypersurfaces with Orbital-Optimized Density Functional Theory

Objective

Modeling light-induced processes is a complex task, but understanding and exploiting them enables employing the absorbed energy in transformations. Yet, no electronic-structure method combines high accuracy with low scaling, limiting the size of the systems investigated in molecular simulations. This project will advance state-specific methods based on density functional theory (DFT), improve the calculation of the excited-state potential energy surface (PES), and apply them to the direct calculation of experimental observables in molecular simulations. During the outgoing phase at UC Berkeley, under the supervision of Prof. Martin Head-Gordon, I will develop electronic structure methods to accurately model atomic forces and structures with orbital-optimized density functional theory (OO-DFT). The OO-DFT PES is corrected in the crossing regions with the non-orthogonal configuration interaction (NOCI) method, and the off-diagonal NOCI Hamiltonian elements approximate electronic couplings for energy and charge transfer. Furthermore, the transient-absorption spectra (TA) will be computed via time-dependent perturbation of the excited-state density, enabling direct comparison to time-resolved spectroscopy experiments. Each method development task will be validated by systematic benchmarking, and all reference sets will be deposited in open-access repositories. During the return phase at the Donostia International Physics Center, under the supervision of Prof. David Casanova, I will apply the excited-state methods I developed to photoactive systems of technological and biological relevance, including organic photovoltaics (OPV), organic light-emitting diodes (OLED), and photosynthetic complexes. The results will broaden our understanding of natural light-harvesting and accelerate sustainable technologies. Dissemination will target excited-state simulation groups, exploitation with partners in the OPV and OLED sectors, and outreach will engage citizens in public events.