Ab initio finite oligomer method for nonlinear optical properties of conjugated polymers. Effect of electron correlation on the static longitudinal hyperpolarizability of polyacetylene

Toto, Teressa Tangredi; Toto, Joseph L.; Melo, Celso P. de; Hasan, Muhammad

doi:10.1016/0009-2614(95)00907-l

Cited by 102 publications

(53 citation statements)

References 26 publications

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“…From the HF-based ab initio studies [15] on the NLO properties of PA chains, it is known that even simple HF theory provides results which are in qualitative agreement with the more advanced [16] Møller-Plesset (MP) and coupled cluster calculations. The problem with the LDA and GGA xc potentials can be clarified by comparing the LDA and HF results for a and g of PA chains ͑C 2n H 2n12 ͒, with a varying number of unit cells n. This is done in Fig.…”

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confidence: 78%

Electric Field Dependence of the Exchange-Correlation Potential in Molecular Chains

et al. 1999

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Density functional calculations on the (non)linear optical properties of conjugated molecular chains using currently popular exchange-correlation (xc) potentials give overestimations of several orders of magnitude. By analyzing "exact" and Krieger-Li-Iafrate xc potentials, the error is traced back to an incorrect electric field dependence of the "response part" of the xc potential in local and gradientcorrected density approximations, which lack a linear term counteracting the applied electric field.PACS numbers: 31.15. Ew, 42.65.An, 71.15.Mb, 77.22.Ej The nonlinear optical (NLO) properties of molecules are of considerable current interest, both from the fundamental and technological points of view [1][2][3]. Prototype systems exhibiting large NLO responses like the polyacetylene (PA) chains have been studied intensively with conventional, ab initio Hartree-Fock (HF) based theoretical techniques [2]. Because density functional theory (DFT) [4,5] usually provides clearly improved accuracy with respect to HF at similar or lower computational cost, it seems tempting to apply DFT to the prediction of the NLO properties of large, conjugated molecular chains.Our calculations on static hyperpolarizabilities (determining the NLO response in the static limit) of such chains show, both here and in Ref. [6], that the local density approximation (LDA) and generalized gradient approximations (GGAs) in DFT provide very poor results. Whereas previously reported LDA errors are typically 10% for dielectric constants, we find overestimations of several orders of magnitude for the second hyperpolarizability g. In view of the respectable accuracy which is usually obtained in DFT calculations, this is highly surprising and deserves a detailed analysis, as this error may be among the largest in the history of DFT calculations. Our analysis allows us to pinpoint the weakness of the LDA. It will be shown below that, if an electric field, E, is applied, the so-called response part of the exact exchange-correlation (xc) potential develops a global behavior counteracting the applied field. Such behavior is not present in the LDA or GGA potentials. Our results substantiate and further elucidate the findings of Gonze, Ghosez, and Godby [7] and others [8][9][10][11][12][13], who pointed out the existence of such a counteracting linear potential in the exact y xc and provided the first physical interpretation for it [10,13].Description of the problem.-For this work, extensive calculations have been performed on PA and hydrogen chains. The LDA results described below have been obtained in the same manner as earlier calculations on the polarizability (a) and second hyperpolarizability (g) of C 60 [14]. Details of the computational procedure, the geometries, etc., have been given in another paper [6], where several aspects of the LDA problem (size of electron correlation correction, effect of bond length alternation) are described more fully.From the HF-based ab initio studies [15] on the NLO properties of PA chains, it is known that even sim...

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confidence: 78%

Electric Field Dependence of the Exchange-Correlation Potential in Molecular Chains

et al. 1999

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“…On this basis KTRH claim to obtain the static HF longitudinal hyperpolarizability per unit cell for the infinite polymer with an uncertainty similar to that found for small molecules, even though the value for the largest oligomer considered ͑C 44 H 46 ͒ was only 43% of the asymptotic result. Subsequent MP2 electron correlation calculations, 22,23 yield an MP2/ RHF ratio for the static longitudinal hyperpolarizability that is essentially constant for all oligomers larger than C 8 H 10 . Thus, in this instance, extrapolation of the correlated value is not a problem once the HF result has been obtained.…”

Section: Introductionmentioning

confidence: 99%

Hartree–Fock static longitudinal (hyper)polarizability of polyyne

Toto

Melo

et al. 1996

The Journal of Chemical Physics

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The evolution in the static longitudinal polarizability and second hyperpolarizability of the C 4 H 2 through C 54 H 2 oligomers of polyyne is studied at the Hartree-Fock level of theory. We find that the calculated values are highly sensitive to the adopted geometry. Using improved geometries, new extrapolation procedures and careful finite field determinations we extend earlier work by others so as to provide reliable estimates for the above properties in the infinite polymer limit.

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“…The organic nonlinear optical materials have many merits, such as relatively low cost, ease of design, and optical susceptibilities comparable to or exceeding those of inorganic crystals [1,6,8,10,14,16,17]. Their p-electron delocalized frameworks have been known as a crucial factor in determining the strength of nonlinear optical response [1].…”

Section: Introductionmentioning

confidence: 99%

“…The (hyper)polarizabilities of the linear p-conjugated organic systems, such as polyene and polyyne oligomers, have attracted much attention for more than 30 years owing to its importance in the design of materials with large nonlinear optical responses [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The organic nonlinear optical materials have many merits, such as relatively low cost, ease of design, and optical susceptibilities comparable to or exceeding those of inorganic crystals [1,6,8,10,14,16,17].…”

Section: Introductionmentioning

confidence: 99%