New-Generation Electron-Propagator Methods for Calculations of Electron Affinities and Ionization Energies: Tests on Organic Photovoltaic Molecules

A new generation of ab initio electron-propagator
self-energies recently superseded its antecedents’ accuracy
and computational efficiency in calculating vertical ionization energies
(VIEs) of closed-shell molecules. (See J. Chem. Phys. 2021, 155, 204107, J. Chem.
Theory Comput. 2022, 18, 4927, J. Chem. Phys. 2023, 159, 124109.)
No adjustable parameters were introduced in the generation of reference
orbitals or in the construction of self-energies. The same approach
has been extended in this work to vertical electron affinities (VEAs).
Calculations were performed on 24 conjugated, organic photovoltaic
molecules with diverse functional groups. These molecules are considerably
larger than those studied in previous tests on VIEs. Several new-generation
self-energies produce mean absolute errors (MAEs) below 0.1 eV versus ΔCCSD(T)
(i.e., total energy differences from the coupled-cluster singles,
doubles, and perturbative triples method) VIEs and VEAs obtained with
identical basis sets. A composite model employs cubically and quintically
scaling algorithms and power-law basis-set extrapolations based on
augmented double–triple or triple-quadruple ζ data. Its
MAEs are near 0.05 eV versus benchmark values, with 0.03 eV error
bars for the lowest VIE and the highest VEA of each molecule. A more
efficient and equally accurate composite model for calculating VIEs
avoids full transformations of electron repulsion integrals to the
molecular orbital basis. High probability factors support the diagonal
self-energy approximation, wherein Dyson orbitals are proportional
to canonical, Hartree–Fock orbitals.