The ‘triplet-excited region’ in linear polyenes: Real or artifactual?

Takahashi, Ohgi; Watanabe, Masayuki; Kikuchi, Osamu

doi:10.1016/s0166-1280(98)00595-8

Cited by 4 publications

(4 citation statements)

References 11 publications

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“…The authors related this central domain of diminishing bond alternation to bond orders and postulated a “triplet-excited” region. Subsequent investigations by Takahasi et al , pointed out the deficiencies in this approach: Their single-excitation CI (SCI) calculations on the series of polyenes from C 8 H 18 to C 22 H 46 yielded geometries in agreement with Kuki et al However, comparison calculations with CASSCF on octatetraene gave a considerably different bond alternation pattern which is consistent with our present calculations. Takahashi et al concluded the appearance of the postulated “triplet-excited region” to be artifactual in SCI and SDCI calculations, related to the use of RHF MOs in combination with limitations on the excitations in the CI space.…”

Section: Resultssupporting

confidence: 88%

“…77,78 pointed out the deficiencies in this approach: Their single-excitation CI (SCI) calculations on the series of polyenes from C 8 H 18 to C 22 H 46 yielded geometries in agreement with Kuki et al However, comparison calculations with CASSCF on octatetraene gave a considerably different bond alternation pattern which is consistent with our present calculations. Takahashi et al…”

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confidence: 88%

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Performance of the Density Functional Theory/Multireference Configuration Interaction Method on Electronic Excitation of Extended π-Systems

Marian

Gilka

2008

J. Chem. Theory Comput.

173

198

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The combined density functional theory/multireference configuration interaction (DFT/MRCI) method [Grimme and Waletzke. J. Chem. Phys. 1999, 111, 5645] has been employed to study the 1 L a and 1 L b states of linear polyacenes and the low-lying triplet and singlet states of linear polyenes and diphenyl-polyenes. We have systematically investigated the dependence of the electronic state properties on technical parameters of the calculations such as the atomic orbital basis set or the geometry optimization approach. The choice of basis set appears to be of minor importance whereas the excitation energies of the polyenes are quite sensitive to the ground-state geometry parameters. The DFT/MRCI energies at the B3-LYP optimized geometries systematically underestimate the experimental values, but we do not observe a bias toward one or the other type of state. The energy gaps between the electronically excited states are reproduced very well. In particular, this applies also to the first excited singlet 2 1 A g and the optically bright 1 B u + state of the polyenes. The latter appears to be the S 3 or even S 4 state in longer polyenes where the multiconfigurational 1 B u state represents S 2 . Frequencies and intensities of the excited-state absorption from the 2 1 A g state are found to be strongly geometry dependent.

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Section: Resultssupporting

confidence: 88%

supporting

confidence: 88%

Performance of the Density Functional Theory/Multireference Configuration Interaction Method on Electronic Excitation of Extended π-Systems

Marian

Gilka

2008

J. Chem. Theory Comput.

173

198

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“…This conclusion was later doubted by Takahashi et al, after a comparative study of ab initio SCI calculations on a lot of oligomers against complete-active-space self-consistant-field ͑CASSCF͒ calculations on a shorter member, octatetraene. 7 While the SCI calculations well reproduced the ''triplet-excited region'' in the central part of the chains, CASSCF gave a basically very different geometry; it seems that there exist two independent delocalized regions ͑soliton-antisoliton pair͒ located symmetrically away from the center of the oligomer chain. The inconsistency between CASSCF and SCI computations was ascribed to the insufficient account of electron correlations in ab initio SCI or semiempirical SDCI schemes.…”

Section: Introductionmentioning

confidence: 93%

“…[1][2][3][4][5][6] In theoretical studies, it has been well accepted that in T 1 states, the single and double bonds at the central region are swapped, which makes cis-trans conformation interconversions possible. [5][6][7][8][9] However, there is an interesting disagreement on the details of T 1 -state geometries optimized with different methods. In 1991, Kuki et al performed the Pariser-Parr-Pople ͑PPP͒ SDCI calculations on different lengths of polyene oligomers (C 10 H 12 , C 14 H 16 , C 18 H 20 , and C 22 H 24 ), finding that the bond length alternation disappears only in the central moiety of the polyene oligomer in the triplet excitation from the S 0 ground state; furthermore, the length of this delocalized region kept constant with the oligomer size.…”

Section: Introductionmentioning

confidence: 99%

“Triplet-excited region” in polyene oligomers revisited: Pariser–Parr–Pople model studied with the density matrix renormalization group method

Liu

Jiang

2004

The Journal of Chemical Physics

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We have carried out density matrix renormalization group calculations on the T1 state of linear polyenes applying the Pariser-Parr-Pople (PPP) Model. The geometry optimization for the polyene oligomers C(2n)H(2n+2) (n = 4,5,6,...,15) shows that the S0 to T1 excitation region is composed of a soliton-antisoliton pair located symmetrically away from the center of the chain and leads to single- and double-bond interconversions in between. The distance between the soliton and antisoliton centers in T1 state changes with the length of the chain, contradictory to earlier conclusions obtained with PPP-SDCI or ab initio SCI methods. The inconsistency most possibly comes from the insufficient consideration of the electron correlations in small-scale CI methods.

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Failure of density-functional theory and time-dependent density-functional theory for large extended π systems

Cai

Sendt

Reimers

2002

The Journal of Chemical Physics

329

295

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Density-functional theory ͑DFT͒ is widely used for studying large systems such as metals, semiconductors, and large molecules, with time-dependent density-functional theory becoming a very powerful tool for investigating molecular excited states. As part of a systematic study of both the intrinsic weaknesses of DFT and the weaknesses of present implementations, we consider its application to the one and two-dimensional conjugated systems: polyacetylene fragments and oligoporphyrins, respectively. Very poor results are obtained for the calculated spectra, and polyacetylene is predicted by all functionals considered, including gradient-corrected functionals, to have a triplet ground state. The cause of this is linked to known problems of existing density functionals concerning nonlocality and asymptotic behavior which result in the highest-occupied molecular-orbital being too high in energy so that semiconductors and low-band-gap insulators are predicted to have metal-like properties. The failure of modern density functionals to predict qualitatively realistic molecular hyperpolarizabilities for extended systems is closely related.

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The ‘triplet-excited region’ in linear polyenes: Real or artifactual?

Cited by 4 publications

References 11 publications

Performance of the Density Functional Theory/Multireference Configuration Interaction Method on Electronic Excitation of Extended π-Systems

Performance of the Density Functional Theory/Multireference Configuration Interaction Method on Electronic Excitation of Extended π-Systems

“Triplet-excited region” in polyene oligomers revisited: Pariser–Parr–Pople model studied with the density matrix renormalization group method

Failure of density-functional theory and time-dependent density-functional theory for large extended π systems

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