Interpreting Bonding and Spectra With Correlated, One-Electron Concepts From Electron Propagator Theory

Abstract

Abstract Electron propagator theory provides a strategy with computational and interpretive advantages for the prediction of electron attachment and detachment energies and other properties of molecules and molecular ions. Although the effects of electron correlation may be systematically included up to the exact limit, transparent generalizations of one-electron concepts also are procured by the electron propagator approach to molecular electronic structure. Generalized molecular-orbital concepts emerge from the Dyson quasiparticle equation, including correlated electron binding energies and their Dyson orbitals. This information suffices to predict transition probabilities which are probed in various kinds of spectroscopic and scattering experiments. Relationships between correlated transition and reference-state properties are discussed. Approximations in the self-energy operator, wherein relaxation and correlation effects on electron binding energies reside, are described. Emphasis is placed on approaches that employ a separation between occupied and virtual spin-orbitals such as the renormalized partial third order, the nondiagonal renormalized second order, the second-order transition operator and the Brueckner-doubles, triple-index ionization operator methods. Computational characteristics of these methods are compared with those of older precedents, including the second order, outer valence green function, and GW self-energies. Results of numerical tests on molecules of general interest and improved strategies for treating basis-set effects are reviewed. Recent and noteworthy applications to molecular wires, solvated molecules and ions, gas-phase anions, super-halogens, positron–molecule complexes, anionic resonances, and photoionization cross sections are summarized.