Coupling molecules to the quantized radiation field inside
an optical
cavity creates a set of new photon–matter hybrid states called
polariton states. We combine electronic structure theory with quantum
electrodynamics (QED) to investigate molecular polaritons usingab initiosimulations. This framework joins unperturbed
electronic adiabatic states with the Fock state basis to compute the
eigenstates of the QED Hamiltonian. The key feature of this “parametrized
QED” approach is that it provides the exact molecule–cavity
interactions, limited by only approximations made in the electronic
structure. Using time-dependent density functional theory, we demonstrated
comparable accuracy with QED coupled cluster benchmark results for
predicting potential energy surfaces in the ground and excited states
and showed selected applications to light-harvesting and light-emitting
materials. We anticipate that this framework will provide a set of
general and powerful tools that enable directab initiosimulation of exciton polaritons in molecule–cavity hybrid
systems.