Influence of the Delocalization Error and Applicability of Optimal Functional Tuning in Density Functional Calculations of Nonlinear Optical Properties of Organic Donor–Acceptor Chromophores

Authors

  • Haitao Sun,

    1. Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY 14260-3000 (USA)
    2. Shanghai Key Laboratory of Advanced Polymeric Materials, Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (P. R. China)
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  • Prof. Dr. Jochen Autschbach

    Corresponding author
    1. Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY 14260-3000 (USA)
    • Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY 14260-3000 (USA)
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Abstract

Nonempirically tuned hybrid density functionals with range-separated exchange are applied to calculations of the first hyperpolarizability (β) and charge-transfer (CT) excitations of linear “push–pull” donor–acceptor-substituted organic molecules with extended π-conjugated bridges. An unphysical delocalization with increasing chain length in density functional calculations can be reduced significantly by enforcing an asymptotically correct exchange-correlation potential adjusted to give frontier orbital energies representing ionization potentials. The delocalization error for a number of donor–acceptor systems is quantified by calculations with fractional electron numbers and from orbital localizations. Optimally tuned hybrid variants of the PBE functional incorporating range-separated exchange can produce similar magnitudes for β as Møller–Plesset second-order perturbation (MP2) correlated calculations. Improvements are also found for CT excitation energies, with results similar to an approximate coupled-cluster model (CC2).

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