Electron Propagator Theory of Vertical Electron Detachment Energies of Anions: Benchmarks and Applications to Nucleotides

A new generation of ab initio electron-propagator
self-energy approximations that are free of adjustable parameters
is tested on a benchmark set of 55 vertical electron detachment energies
of closed-shell anions. Comparisons with older self-energy approximations
indicate that several new methods that make the diagonal self-energy
approximation in the canonical Hartree–Fock orbital basis provide
superior accuracy and computational efficiency. These methods and
their acronyms, mean absolute errors (in eV), and arithmetic bottlenecks
expressed in terms of occupied (O) and virtual (V) orbitals are the
opposite-spin, non-Dyson, diagonal second-order method (os-nD-D2,
0.2, OV2), the approximately renormalized quasiparticle
third-order method (Q3+, 0.15, O2V3) and the
approximately renormalized, non-Dyson, linear, third-order method
(nD-L3+, 0.1, OV4). The Brueckner doubles with triple field
operators (BD-T1) nondiagonal electron-propagator method provides
such close agreement with coupled-cluster single, double, and perturbative
triple replacement total energy differences that it may be used as
an alternative means of obtaining standard data. The new methods with
diagonal self-energy matrices are the foundation of a composite procedure
for estimating basis-set effects. This model produces accurate predictions
and clear interpretations based on Dyson orbitals for the photoelectron
spectra of the nucleotides found in DNA.