Orbital Optimized Density Functional Theory for Electronic Excited States

Density
functional theory (DFT) based modeling of electronic excited
states is of importance for investigation of the photophysical/photochemical
properties and spectroscopic characterization of large systems. The
widely used linear response time-dependent DFT (TDDFT) approach is,
however, not effective at modeling many types of excited states, including
(but not limited to) charge-transfer states, doubly excited states,
and core-level excitations. In this perspective, we discuss state-specific
orbital optimized (OO) DFT approaches as an alterative to TDDFT for
electronic excited states. We motivate the use of OO-DFT methods and
discuss reasons behind their relatively restricted historical usage
(vs TDDFT). We subsequently highlight modern developments that address
these factors and allow efficient and reliable OO-DFT computations.
Several successful applications of OO-DFT for challenging electronic
excitations are also presented, indicating their practical efficacy.
OO-DFT approaches are thus increasingly becoming a useful route for
computing excited states of large chemical systems. We conclude by
discussing the limitations and challenges still facing OO-DFT methods,
as well as some potential avenues for addressing them.