### Abstract

Electron binding energies are evaluated as differences in total energy between the N- and (N ± 1)-electron systems calculated by the nth-order Møller-Plesset perturbation (MPn) theory using the same set of orbitals. The MPn energies up to n = 30 are, in turn, obtained by the determinant-based method of Knowles et al. (Chem. Phys. Lett. 1985, 113, 8-12). The zeroth- through third-order electron binding energies thus determined agree with those obtained by solving the Dyson equation in the diagonal and frequency-independent approximations of the self-energy. However, as n → ∞, they converge at the exact basis-set solutions from the Dyson equation with the exact self-energy, which is nondiagonal and frequency-dependent. This suggests that the MPn energy differences define an alternative diagrammatic expansion of Koopmans-like electron binding energies, which takes into account the perturbation corrections from the off-diagonal elements and frequency dependence of the irreducible self-energy. Our analysis shows that these corrections are included as semireducible and linked-disconnected diagrams, respectively, which are also found in a perturbation expansion of the electron binding energies of the equation-of-motion coupled-cluster methods. The rate of convergence of the electron binding energies with respect to n and its acceleration by Padé approximants are also discussed.

Original language | English (US) |
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Pages (from-to) | 1595-1606 |

Number of pages | 12 |

Journal | Journal of Chemical Theory and Computation |

Volume | 11 |

Issue number | 4 |

DOIs | |

State | Published - Apr 14 2015 |

### ASJC Scopus subject areas

- Computer Science Applications
- Physical and Theoretical Chemistry

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## Cite this

*Journal of Chemical Theory and Computation*,

*11*(4), 1595-1606. https://doi.org/10.1021/acs.jctc.5b00005