Dynamical configuration interaction study of free base porphyrin

We apply the recently developed dynamical configuration interaction (DCI) theory to study the low-lying excited states of free base porphyrin. In DCI [1,2], we diagonalize the exact many-body Hamiltonian in the strongly-correlated active space with the wave function technique of configuration interaction (CI). Additionally, the effects of the surrounding degrees of freedom are downfolded onto an energy-dependent correction added to the bare CI Hamiltonian. These corrections are approximated with many-body Green's function theory in the GW approximation. Free-base porphyrin is the largest system studied with DCI so far and serves as an important test of the numerical implementation, scalability, and size consistency of the theory. Our DCI results for excitation energies of porphyrin are in good agreement with past work.

[1] M. Dvorak and P. Rinke. Dynamical configuration interaction: Quantum embedding that combines wave functions and Green's functions, Phys. Rev. B 99, 115134 (2019).
[2] M. Dvorak, D. Golze, and P. Rinke. Quantum embedding theory in the screened Coulomb interaction: Combining configuration interaction with GW/BSE, Phys. Rev. Mat. 3, 070801(R) (2019).