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    Anisotropic Dielectric Screened Range-Separated Hybrid Density Functional Theory Calculations of Charge Transfer States across an Anthracene-TCNQ Donor-Acceptor Interface
    (Amer Chemical Soc, 2024) Chakravarty, Chandrima; Saller, Maximilian A. C.; Aksu, Huseyin; Dunietz, Barry D.
    A density functional theory framework is developed to study electronic excited states affected by an anisotropic dielectric environment. In particular, an anisotropic dielectric screened range-separated hybrid (SRSH[r]) functional is defined and combined with an anisotropic polarizable continuum model (PCM) implemented through a generalized Poisson equation solver. We develop the SRSH-PCM(r) approach and use it to quantify the effect of anisotropy on an excited charge transfer (CT) state energy. In particular, the dielectric interface effect on the CT state within a donor-acceptor molecular complex of antrancene and tetracyanoquinodimethane is studied. The donor-acceptor complex and the dielectric interface are used to represent the interface between thin films consisting of these materials. We report the effect of such a dielectric interface on the energy of a CT and follow its dependence on the donor-acceptor distance. We also benchmark the anisotropy-affected energy by comparing to homogeneous dielectric calculated energies. Due to the planar interface, the anisotropic energies are expected to to match with those obtained based on isotropic calculations of the larger dielectric constant at large enough distances. The approach is applicable, in general, to more complicated dielectric constant distributions as expected to be found in actual interfaces of such thin films or in other systems, for example, for CT processes within photosystems.
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    Öğe
    Electronic Spectra of C60Films Using Screened Range Separated Hybrid Functionals
    (American Chemical Society, 2021) Chakravarty, Chandrima; Aksu, Hüseyin; Maiti, Buddhadev; Dunietz, Barry D.
    We study computationally the electronic spectra of C60thin films using the recently developed density functional theory (DFT) framework combining a screened range separated hybrid (SRSH) functional with a polarizable continuum model (PCM). The SRSH-PCM approach achieves excellent correspondence between the frontier orbital’s energy levels and the ionization potential and electron affinity of the molecular systemat the condensed phaseand consequently leads to high quality electronic excitation energies when used in time-dependent DFT calculations. Our calculated excited states reproduce the experimentally main reported spectral peaks at the 3.6-4.6 eV energy range and when addressing excitonic effects also reproduce the red-shifted spectral feature. Notably, we analyze the low-lying peak at 2.7 eV and associate it to an excitonic state.