Fourth-Order Algebraic Diagrammatic Construction for\nElectron Detachment and Attachment: The IP- and EA-ADC(4) Methods

We present a non-Dyson\nfourth-order algebraic diagrammatic construction\nformulation of the electron propagator, featuring the distinct IP-\nand EA-ADC(4) schemes for the treatment of ionization and electron\nattachment processes. The algebraic expressions have been derived\nautomatically using the intermediate state representation approach\nand implemented in the Q-Chem quantum-chemical program package.\nThe performance of the novel methods is assessed with respect to high-level\nreference data for ionization potentials and electron affinities of\nclosed- and open-shell systems. While only minor improvements over\nthe corresponding third-order methods are observed for one-hole ionization\nand one-particle electron attachment processes from closed-shell systems\n(MAE<sub>IP‑ADC(4)</sub> = 0.27 eV and MAE<sub>EA‑ADC(4)</sub> = 0.05 eV), a significantly enhanced performance is found in case\nof open-shell reference states (MAE<sub>IP‑ADC(4)</sub> = 0.11\neV and MAE<sub>EA‑ADC(4)</sub> = 0.02 eV). A particularly appealing\nfeature of the novel methods is their accurate treatment of satellite\ntransitions. For closed-shell reference states, we obtain accuracies\nof MAE<sub>IP‑ADC(4)</sub> = 0.81 eV and MAE<sub>EA‑ADC(4)</sub> = 0.27 eV, while in case of open-shell reference states, mean absolute\nerrors of MAE<sub>IP‑ADC(4)</sub> = 0.15 eV and MAE<sub>EA‑ADC(4)</sub> = 0.27 eV are found.