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Abstract:
We investigate charge transfer in prototypical molecular donor-acceptor compounds using hybrid
density functional theory (DFT) and the GW approximation at the perturbative level (G0W0) and at
full self-consistency (sc-GW). For the systems considered here, no charge transfer should be expected
at large intermolecular separation according to photoemission experiment and accurate quantumchemistry
calculations. The capability of hybrid exchange-correlation functionals of reproducing
this feature depends critically on the fraction of exact exchange α, as for small values of α spurious
fractional charge transfer is observed between the donor and the acceptor. G0W0 based on hybrid
DFT yields the correct alignment of the frontier orbitals for all values of α. However, G0W0 has
no capacity to alter the ground-state properties of the system, because of its perturbative nature.
The electron density in donor-acceptor compounds thus remains incorrect for small values. In
sc-GW, where the Green’s function is obtained from the iterative solution of the Dyson equation,
the electron density is updated and reflects the correct description of the level alignment at the GW
level, demonstrating the importance of self-consistent many-body approaches for the description of
ground- and excited-state properties in donor-acceptor systems.
