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Determination of Correlation Parameters in π-Conjugated Polymers

Published online by Cambridge University Press:  25 February 2011

J. Tinka Gammel ,
D.K. Campbell ,
E.Y. Loh Jr. ,
S. Mazumdar  and
S.N. Dixit
J. Tinka Gammel
Affiliation:
Theoretical Division and Center for Nonlinear Studies Los Alamos National Laboratory, Los Alamos, NM 87545
D.K. Campbell
Affiliation:
Theoretical Division and Center for Nonlinear Studies Los Alamos National Laboratory, Los Alamos, NM 87545
E.Y. Loh Jr.
Affiliation:
Theoretical Division and Center for Nonlinear Studies Los Alamos National Laboratory, Los Alamos, NM 87545
S. Mazumdar
Affiliation:
Department of Physics, University of Arizona, Tucson, AZ 85721
S.N. Dixit
Affiliation:
Lawrence Livermore National Laboratory, Livermore, CA 94550
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Abstract

Using exact finite-size diagonalizations of extended Peierls-Hubbard Hamiltonians for systems of up to 15 sites, we study the excited state spectra of models for the finite oligomer analogs of trans– and cis– polyacetylene. We use a novel “phase randomization” technique and a variety of other methods to extract maximal information from these small systems. For several electron-phonon couplings in the expected range, we discuss the extent to which we are able to find consistent values of the Hubbard on-site (U) and nearest-neighbor (V) correlation parameters such that the band gap, the 2 1Ag state, optical phonon frequency, and the optical absorptions for charged and neutral solitons and dimers occur in the experimentally expected ranges. Our results suggest that these correlation parameters are in the intermediate coupling regime (U ⋍ 2.5t0), beyond the range of perturbation theory.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 173: Symposium Q – Advanced Organic Solid State Materials , 1989 , 419
Copyright
Copyright © Materials Research Society 1990

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References

REFERENCES

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