Renormalization of Molecular Electronic Levels at Metal-Molecule Interfaces

Abstract

The electronic structure of benzene on graphite (0001) is computed using the GW approximation for the electron self-energy. The benzene quasiparticle energy gap is predicted to be 7.2 eV on graphite, substantially reduced from its calculated gas-phase value of 10.5 eV. This decrease is caused by a change in electronic correlation energy, an effect completely absent from the corresponding Kohn-Sham gap. For weakly coupled molecules, this correlation energy change can be described as a surface polarization effect. A classical image potential model illustrates the impact for other conjugated molecules on graphite.

Charge Separation in Donor–C60 Complexes with Real-Time Green Functions: The Importance of Nonlocal Correlations

“…The gap closure in the equilibrium case is of relevance in, e.g., estimating the conductance of a molecular junction. 44,45,48,49 The gap opening in the photoexcited case is instead of relevance to CS since the formation of a CT exciton strongly depends upon level alignment. Both types of gap renormalization are captured by the second-Born (2B) approximation to the self-energy.…”

Impact of derivatization on electron transmission through dithienylethene-based photoswitches in molecular junctions

“…GGA functionals like this one are known to underestimate molecular HOMO-LUMO gaps, because of the lack of derivative discontinuity. Incidentally, this gap reduction can account for molecular gap renormalization in the vicinity of metal surface by image effects [2]. However, this renormalization can be excessive and leads, in transmission calculations, to current overestimation by positioning the transmission peaks originating from frontier MOs too close to the Fermi level.…”

Optical properties of bulk semiconductors and graphene/boron nitride: The Bethe-Salpeter equation with derivative discontinuity-corrected density functional energies

“…For molecules on surfaces, this effect has been shown to be well described by the GW method, whereas both (semi-)local and hybrid functionals completely miss the effect predicting no change in the gap upon adsorption (apart from obvious hybridization effects). 61,62 Interestingly, within the GLLBSC the gap reduction is a result of the vanishing, or strong reduction, of the derivative discontinuity. However, this also has the unphysical consequence that the reduction is present independent of the graphene-BN distance.…”