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Assessment of density functional theory based Delta SCF (self-consistent field) and linear response methods for longest wavelength excited states of extended pi-conjugated molecular systems

Abstract : Computational investigation of the longest wavelength excitations in a series of cyanines and linear n-acenes is undertaken with the use of standard spin-conserving linear response time-dependent density functional theory (TD-DFT) as well as its spin-flip variant and a Delta SCF method based on the ensemble DFT. The spin-conserving linear response TD-DFT fails to accurately reproduce the lowest excitation energy in these pi-conjugated systems by strongly overestimating the excitation energies of cyanines and underestimating the excitation energies of n-acenes. The spin-flip TD-DFT is capable of correcting the underestimation of excitation energies of n-acenes by bringing in the non-dynamic electron correlation into the ground state; however, it does not fully correct for the overestimation of the excitation energies of cyanines, for which the non-dynamic correlation does not seem to play a role. The ensemble DFT method employed in this work is capable of correcting for the effect of missing non-dynamic correlation in the ground state of n-acenes and for the deficient description of differential correlation effects between the ground and excited states of cyanines and yields the excitation energies of both types of extended pi-conjugated systems with the accuracy matching high-level ab initio multireference calculations. (C) 2014 AIP Publishing LLC.
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https://hal-amu.archives-ouvertes.fr/hal-01415171
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Submitted on : Monday, December 12, 2016 - 6:49:32 PM
Last modification on : Thursday, December 5, 2019 - 10:40:03 AM

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Michael Filatov, Miquel Huix-Rotllant. Assessment of density functional theory based Delta SCF (self-consistent field) and linear response methods for longest wavelength excited states of extended pi-conjugated molecular systems. Journal of Chemical Physics, American Institute of Physics, 2014, 141 (2), pp.024112. ⟨10.1063/1.4887087⟩. ⟨hal-01415171⟩

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