Optical excitations in nanographenes from the Bethe-Salpeter equation and time-dependent density functional theory: absorption spectra and spatial descriptors

Abstract

The GW plus Bethe-Salpeter equation (GW-BSE) formalism is a well-established approach for calculating excitation energies and optical spectra of molecules, nanostructures, and crystalline materials. We implement GW-BSE in the CP2K code and validate the implementation for a standard organic molecular test set, obtaining excellent agreement with reference data, with a mean absolute error in excitation energies below 3 meV. We then study optical spectra of nanographenes of increasing length, showing excellent agreement with experiment. We further compute the size of the excitation of the lowest optically active excitation which converges to about 7.6 $\mathring{A}$ with increasing length. Comparison with time-dependent density functional theory using functionals of varying exact-exchange fraction shows that none reproduce both the size of the excitation and optical spectra of GW-BSE, underscoring the need for many-body methods for accurate description of electronic excitations in nanostructures.

References in corpus (27)

• Many-body perturbation theory calculations using the yambo code
• First-principles GW calculations for fullerenes, porphyrins, phtalocyanine, and other molecules of interest for organic photovoltaic applications
• The GW compendium: A practical guide to theoretical photoemission spectroscopy
• The Ground State Correlation Energy of the Random Phase Approximation from a Ring Coupled Cluster Doubles Approach
• Ultrafast transition between exciton phases in van der Waals heterostructures
• The Bethe-Salpeter Equation Formalism: From Physics to Chemistry
• Quasi-Particle Self-Consistent $GW$ for Molecules
• Towards GW Calculations on Thousands of Atoms
• Reference Energies for Intramolecular Charge-Transfer Excitations
• Real-time GW: Toward an ab initio description of the ultrafast carrier and exciton dynamics in two-dimensional materials
• Topologically localized excitons in single graphene nanoribbons
• Electron-hole and plasmon excitations in 3d transition metals: Ab initio calculations and inelastic x-ray scattering measurements
• Growth optimization and device integration of narrow-bandgap graphene nanoribbons
• Exact relationships between the GW approximation and equation-of-motion coupled-cluster theories through the quasi-boson formalism
• Optical Excitations and Field Enhancement in Short Graphene Nanoribbons
• Connections between many-body perturbation and coupled-cluster theories
• Transferable screened range-separated hybrid functionals for electronic and optical properties of van der Waals materials
• Reference CC3 Excitation Energies for Organic Chromophores: Benchmarking TD-DFT, BSE/$GW$ and Wave Function Methods
• Excitons and carriers in transient absorption and time-resolved ARPES spectroscopy: an abinitio approach
• Probing correlations in the exciton landscape of a moiré heterostructure
• Optical absorption spectra of metal oxides from time-dependent density functional theory and many-body perturbation theory based on optimally-tuned hybrid functionals
• Fast evaluation of solid harmonic Gaussian integrals for local resolution-of-the-identity methods and range-separated hybrid functionals
• A Guide to Molecular Properties from the Bethe-Salpeter Equation
• Fully Analytic Nuclear Gradients for the Bethe--Salpeter Equation
• Linear and Nonlinear Optical Properties of Molecules from Real-Time Propagation Based on the Bethe-Salpeter Equation
• Analytic $G_0{W}_0$ gradients based on a double-similarity transformation equation-of-motion coupled-cluster treatment
• Gaussian basis sets for all-electron excited-state calculations of large molecules