Design of low band gap polymers employing density functional theory?hybrid functionals ameliorate band gap problem

Salzner, Ulrike; Lagowski, Jolanta B.; Pickup, Peter G.; Poirier, Raymond A.

doi:10.1002/(sici)1096-987x(19971130)18:15<1943::aid-jcc9>3.0.co;2-o

Cited by 157 publications

(151 citation statements)

References 30 publications

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“…This basis set has been tested extensively and has been shown to yield reliable results for geometries and excited states of neutral polyenes as well as other conjugated oligomers. 43,[51][52][53][54] As cations and excited states of cations have compact electron densities, 15 this basis set is sufficient for all properties of interest in the present investigation.…”

Section: Methodsmentioning

confidence: 99%

Theoretical Investigation of Excited States of Large Polyene Cations as Model Systems for Lightly Doped Polyacetylene

Salzner

2006

J. Chem. Theory Comput.

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Electronic excitations of polyene cations with chain lengths of up to 101 CH units were investigated as model systems for lightly doped polyacetylene (PA). Since high level ab initio calculations such as complete active space perturbation theory (CASPT2) are limited to systems with about 14 CH units, the performances of time-dependent Hartree-Fock (TDHF) and time-dependent density functional theory (TDDFT) were evaluated. It turned out that TDDFT excitations energies are much more accurate for polyene cations than for neutral polyenes. The difference between TDHF and TDDFT excitation energies for the first allowed excited state of C 49 H 51 + is only 0.30 eV with pure DFT and 0.21 eV with a hybrid functional. For open-shell systems, pure DFT is found to be superior to DFT-hybrid functionals because it does not suffer from spin-contamination. Pure TDDFT excitation energies and oscillator strengths for small openshell polyene cations compare well with high level ab initio results. Excitation energies are found to be almost independent of the geometry, i.e., the size of the defect. Localization of the defect, however, shifts oscillator strengths from the HOMO-LUMO transition to higher lying excited states of the same symmetry. Lightly doped PA is predicted to exhibit several strong absorptions below 1 eV.

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Section: Methodsmentioning

confidence: 99%

Theoretical Investigation of Excited States of Large Polyene Cations as Model Systems for Lightly Doped Polyacetylene

Salzner

2006

J. Chem. Theory Comput.

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“…Next we list the G 0 W 0 results for the corresponding starting point, and finally the results from the internally consistent PBEh (columns on the right). We include also specific literature results obtained with the oft-employed hybrid functional B3LYP [78]. The experimental values are listed in the central column.…”

Section: B Ip Of the Transacetylene Oligomer Seriesmentioning

confidence: 99%

Length dependence of ionization potentials of transacetylenes: Internally consistent DFT/GWapproach

et al. 2015

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We follow the evolution of the ionization potential (IP) for the paradigmatic quasi-one-dimensional transacetylene family of conjugated molecules, from short to long oligomers and to the infinite polymer transpolyacetylene (TPA). Our results for short oligomers are very close to experimental available data. We find that the IP varies with oligomer length and converges to the given value for TPA with a smooth, coupled inverse-length-exponential behavior. Our prediction is based on an "internally consistent" scheme to adjust the exchange mixing parameter α of the PBEh hybrid density functional, so as to obtain a description of the electronic structure consistent with the quasiparticle approximation for the IP. This is achieved by demanding that the corresponding quasiparticle correction, in the GW @PBEh approximation, vanishes for the IP when evaluated at PBEh(α ic ). We find that α ic is also system-dependent and converges with increasing oligomer length, enabling the dependence of the IP and other electronic properties to be identified.

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“…Although the time-dependent GKS equations have yet to be formally derived, hybrid functionals are already widely used for calculating optical properties. For gas-phase molecules, hybrid functionals can improve optical excitation energies, although standard hybrids still do not provide for accurate single-particle excitation energies [13][14][15]18]. TDDFT using the Heyd-Scuseria-Ernzerhof (HSE) short-range hybrid func-tional [32], where non-local exchange is introduced only in the short-range, can improve the absorption spectra of semiconductors and insulators [33], although some discrepancies remain.…”

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confidence: 99%

Solid-state optical absorption from optimally tuned time-dependent range-separated hybrid density functional theory

et al. 2015

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We present a framework for obtaining reliable solid-state charge and optical excitations and spectra from optimally-tuned range-separated hybrid density functional theory. The approach, which is fully couched within the formal framework of generalized Kohn-Sham theory, allows for accurate prediction of exciton binding energies. We demonstrate our approach through first principles calculations of one-and two-particle excitations in pentacene, a molecular semiconducting crystal, where our work is in excellent agreement with experiments and prior computations. We further show that with one adjustable parameter, set to produce an accurate bandgap, this method accurately predicts band structures and optical spectra of silicon and lithium flouride, prototypical covalent and ionic solids. Our findings indicate that for a broad range of extended bulk systems, this method may provide a computationally inexpensive alternative to many-body perturbation theory, opening the door to studies of materials of increasing size and complexity.

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Design of low band gap polymers employing density functional theory?hybrid functionals ameliorate band gap problem

Cited by 157 publications

References 30 publications

Theoretical Investigation of Excited States of Large Polyene Cations as Model Systems for Lightly Doped Polyacetylene

Theoretical Investigation of Excited States of Large Polyene Cations as Model Systems for Lightly Doped Polyacetylene

Length dependence of ionization potentials of transacetylenes: Internally consistent DFT/GWapproach

Solid-state optical absorption from optimally tuned time-dependent range-separated hybrid density functional theory

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