Universal Health Care for Wave Functions

The ground state variational principle is arguably the most important tool in quantum chemistry, as it allows one to diagnose and correct problems in approximate ground state wave functions. Indeed, this principle is relied upon directly or indirectly by essentially every method in quantum chemistry, from density functional theory to perturbation theory to coupled cluster. Unfortunately, a historical lack of excited state variational principles has led to a situation in which excited state theories in quantum chemistry are fundamentally more approximate than their ground state counterparts. This inequity has, among other difficulties, limited the predictive power that chemists can exert over charge transfer processes, excited state absorption experiments, core excitations, and materials spectra. Seeking to address these problems, we have developed rigorous variational principles that are equally applicable to ground and excited states. This seminar will discuss the development of these new approaches, how they can be practically applied to molecules and solids, and how they might be used to make whole areas of quantum chemistry more equitable in their treatment of ground and excited states.

Speaker:  Eric Neuscamman, UC Berkeley