Impact of exact exchange in the description of the electronic structure of organic charge-transfer molecular crystals

Alexandr Fonari, Christopher Sutton, Jean-Luc Bredas, Veaceslav Coropceanu

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21 Scopus citations

Abstract

We evaluate the impact that the amount of nonlocal Hartree-Fock (%HF) exchange included in a hybrid density functional has on the microscopic parameters (transfer integrals, band gaps, bandwidths, and effective masses) describing charge transport in high-mobility organic crystals. We consider both crystals based on a single molecule, such as pentacene, and crystals based on mixed-stack charge-transfer systems, such as dibenzo-TTF–TCNQ. In the pentacene crystal, the band gap decreases and the effective masses increase linearly with an increase in the amount of %HF exchange. In contrast, in the charge-transfer crystals, while the band gap increases linearly, the effective masses vary only slightly with an increase in %HF exchange. We show that the superexchange nature of the electronic couplings in charge-transfer systems is responsible for this peculiar evolution of the effective masses. We compare the density functional theory results with results obtained within the G0W0 approximation as a way of benchmarking the optimal amount of %HF exchange needed in a given functional.
Original languageEnglish (US)
JournalPhysical Review B
Volume90
Issue number16
DOIs
StatePublished - Oct 21 2014
Externally publishedYes

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