Benchmarking GW against exact diagonalization for semi-empirical models

Abstract

We calculate groundstate total energies and single-particle excitation energies of seven pi conjugated molecules described with the semi-empirical Pariser-Parr-Pople (PPP) model using self-consistent many-body perturbation theory at the GW level and exact diagonalization. For the total energies GW captures around 65% of the groundstate correlation energy. The lowest lying excitations are overscreened by GW leading to an underestimation of electron affinities and ionization potentials by approximately 0.15 eV corresponding to 2.5%. One-shot G_0W_0 calculations starting from Hartree-Fock reduce the screening and improve the low-lying excitation energies. The effect of the GW self-energy on the molecular excitation energies is shown to be similar to the inclusion of final state relaxations in Hartree-Fock theory. We discuss the break down of the GW approximation in systems with short range interactions (Hubbard models) where correlation effects dominate over screening/relaxation effects. Finally we illustrate the important role of the derivative discontinuity of the true exchange-correlation functional by computing the exact Kohn-Sham levels of benzene.

9 pages, 5 figures, accepted for publication in Phys. Rev. B

References in corpus (10)

• Renormalization of Molecular Electronic Levels at Metal-Molecule Interfaces
• Ab initio GW many-body effects in graphene
• Fully selfconsistent GW calculations for molecules
• Polarization-induced renormalization of molecular levels at metallic and semiconducting surfaces
• Conserving GW scheme for nonequilibrium quantum transport in molecular contacts
• Optical excitations in organic molecules, clusters and defects studied by first-principles Green's function methods
• Renormalization of Molecular Quasiparticle Levels at Metal-Molecule Interfaces: Trends Across Binding Regimes
• Successes and Failures of Kadanoff-Baym Dynamics in Hubbard Nanoclusters
• Impact of Exchange-Correlation Effects on the IV Characteristics of a Molecular Junction
• GW approach to Anderson model out of equilibrium: Coulomb blockade and false hysteresis in the I-V characteristics

Cited by in corpus (15)

• First-principles GW calculations for fullerenes, porphyrins, phtalocyanine, and other molecules of interest for organic photovoltaic applications
• Fully selfconsistent GW calculations for molecules
• A Benchmark of GW Methods for Azabenzenes: Is the GW Approximation Good Enough?
• First-principles GW calculations for DNA and RNA nucleobases
• Quasi-Particle Self-Consistent $GW$ for Molecules
• All-electron GW calculation for molecules: Ionization energy and electron affinity of conjugated molecules
• Ab initio complex band structure of conjugated polymers: Effects of hydrid DFT and GW schemes
• Image charge effects in single-molecule junctions: Breaking of symmetries and negative differential resistance in a benzene transistor
• Static correlation beyond the random phase approximation: Dissociating H2 with the Bethe-Salpeter equation and time-dependent GW
• Image-charge induced localization of molecular orbitals at metal-molecule interfaces: Self-consistent GW calculations
• Parquet approximation for molecules: spectrum and optical conductivity of the Pariser-Parr-Pople model
• Analytic evaluation of the electronic self-energy in the GW approximation for two electrons on a sphere
• GW approximations and vertex corrections on the Keldysh time-loop contour: application for model systems at equilibrium
• $GW$ self-screening error and its correction using a local density functional
• Broken symmetry solutions in one-dimensional lattice models via many-body perturbation theory