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Influence of the Delocalization Error and Applicability of Optimal Functional Tuning in Density Functional Calculations of Nonlinear Optical Properties of Organic Donor–Acceptor Chromophores
Author(s) -
Sun Haitao,
Autschbach Jochen
Publication year - 2013
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201300256
Subject(s) - hyperpolarizability , delocalized electron , hybrid functional , density functional theory , chromophore , chemistry , coupled cluster , acceptor , molecular physics , perturbation theory (quantum mechanics) , ionization , molecule , time dependent density functional theory , computational chemistry , nonlinear system , chemical physics , nonlinear optical , physics , quantum mechanics , ion , photochemistry , organic chemistry
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).