Optimized Ensemble Time-Dependent Density Functional Theory*

The recent discovery of unphysical divergences in approximate
single-state response theories has underscored the need for more robust
excited-state electronic structure methods. I will present an optimized
ensemble (oe) extension of time-dependent density functional (TDDFT)
theory which produces excited state properties free of artificial
divergences while retaining desirable features of single-state TDDFT
such as orthogonality and computational efficiency. I will explain how
oe-TDDFT reduces self-interaction error in charge-transfer excited
states and can yield conical intersections with the ground state with
correct topology.