We use the ab initio polariton approach we developed in a previous work, which we refer to as the parametrized-QED (pQED) approach. The pQED approach uses the Pauli-Fierz Hamiltonian in the Born-Oppenheimer approximation (see Eq. 2) to describe light and matter interactions and use adiabatic electronic states as the basis for the electronic degrees of freedom and Fock states as the basis for the photonic degree of freedom.