A Mean Field Platform for Excited State Quantum Chemistry

TL;DR

This paper introduces a mean field theory for excited states that parallels ground state Hartree-Fock, enabling efficient and accurate excited state calculations with potential for further correlation methods.

Contribution

It develops a deterministic, variational mean field approach for excited states, analogous to Hartree-Fock, and demonstrates its high accuracy with a paired perturbation theory.

Findings

Outperforms configuration interaction singles in accuracy.

Rivals equation of motion coupled cluster in tested molecules.

Maintains Hartree-Fock-like computational scaling.

Abstract

We present a mean field theory for excited states that is broadly analogous to ground state Hartree-Fock theory. Like Hartree-Fock, our approach is deterministic, state-specific, applies a variational principle to a minimally correlated ansatz, produces energy stationary points, relaxes the orbital basis, has a Fock-build cost-scaling, and can serve as the foundation for correlation methods such as perturbation theory and coupled cluster theory. To emphasize this last point, we pair our mean field approach with an excited state analogue of second order Moller-Plesset theory and demonstrate that in water, formaldehyde, neon, and stretched lithium fluoride, the resulting accuracy far exceeds that of configuration interaction singles and rivals that of equation of motion coupled cluster.