Dyson orbitals electron propagator calculations

Electron propagator theory generates a one-electron picture of electronic structure that includes electron correlation. One-electron energies may be obtained reliably for closed-shell molecules with the P3 method and more complex correlation effects can be treated with renormalized reference states and orbitals. To each electron binding energy, there corresponds a Dyson orbital that is a correlated generalization of a canonical molecular orbital. Electron propagator theory enables interpretation of precise ab initio calculations in terms of one-electron concepts. 

The lowest, virtual, canonical HF orbitals of the neutrals consist chiefly of valence s and p basis functions. Singly occupied spin orbitals that occur only in UHF calculations on the anion are composed of the same AOs. Both types of these one-electron wave funetions may be considered approximations to the Dyson orbitals [85,86] corresponding to the EAs of the beryllium clusters. In the framework of the electron propagator theory [85], the Dyson orbitals are overlaps between an N-electron reference state and final states with N electrons. They form an overcomplete set and are not necessarily normalized to unity. 

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