Accurate Evaluation of Real-Time Density Functional Theory Providing Access to Challenging Electron Dynamics

Abstract

We demonstrate that electronic excitations and their transition densities can be obtained from real-time density functional theory calculations with great accuracy by relating the data from numerical propagation to the analytical form of the electronic response after a boost excitation. The latter is derived in this article. This approach facilitates quantitatively obtaining oscillator strengths, identifying excitations that carry very small oscillator strengths, and assessing electronic couplings from transition densities based on comparatively short propagation times. These features are of interest in particular for studying light-harvesting systems. For demonstration purposes, we study the Q band excitations of bacteriochlorophyll a (BChl a) and calculate coupling strengths between two BChl a's to check the validity of the dipole-dipole and pure Coulomb coupling mechanisms. For further illustration, we investigate the paradigm test system Na and the coupling between two Na dimers.

Nonequilibrium Solvent Polarization Effects in Real-Time Electronic Dynamics of Solute Molecules Subject to Time-Dependent Electric Fields: A New Feature of the Polarizable Continuum Model

“…We extract the optical absorption cross section matrix Σ ij at the energy of the transition B, and we diagonalize it. For a nondegenerate band, we expect just one eigenvalue different from zero, and since , 22,34 the normalized eigenvector associated with the nonzero eigenvalue would set the direction for the TDM, d 0B . If in turn the band is almost degenerate, we can still find the TDMs with the largest contributions to the absorption by diagonalizing the cross-section matrix and taking the eigenvectors associated with the highest eigenvalues.…”

Ultranonlocality and accurate band gaps from a meta-generalized gradient approximation

“…All calculations for the H 8 −H 8 charge-transfer system were performed spin polarized, self-consistently on a realspace grid with BTDFT [40] using Troullier-Martins LDA pseudopotentials [137], ellipsoidal boundaries with semiaxis of 20a 0 perpendicular to and 32a 0 along the chains, and a grid spacing of 0.3a 0 . For the KS iterations, an energy convergence criterion of 5 × 10 −6 E h was used.…”

“…The chromophores in turn are typically embedded in a protein matrix, at least parts of which should also be taken into account explicitly [33,[35][36][37]. However, semilocal functionals are currently at their limits for such systems due to their inability to properly describe charge transfer [38][39][40]. Therefore, there is a serious need for functionals that do not suffer from the large, qualitative errors that traditional semilocal functionals plague, yet come at a comparable computational price.…”

Environment effects on X-ray absorption spectra with quantum embedded real-time Time-dependent density functional theory approaches

“…where δ ρ(r, ω) is the Fourier Transform of the timedependent (TD) induced density δρ(r, t) = ρ(r, t) − ρ(r, 0). Many research groups have recently contributed to this topic [97][98][99][100] , focusing on low-frequency excitations.…”