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First-Principles Study of Soliton Hyperfine Interactions in Polyacetylene

Published online by Cambridge University Press:  26 February 2011

C. T. White
Affiliation:
Theoretical Chemistry Section, Naval Research Laboratory, Washington, DC 20375
F. W. Kutzler
Affiliation:
Department of Chemistry, Tennessee Technical University, Cookeville, TN 38505
J. W. Mintmire
Affiliation:
Theoretical Chemistry Section, Naval Research Laboratory, Washington, DC 20375
M. R. Cook
Affiliation:
Department of Chemical Engineering, University of Massachusetts, Amherst, MA 01003
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Abstract

All-trans-polyacetylene is considered the prototypical broad band gap quasi onedimensional organic semiconductor. Intrinsicsoliton defects have long been known to be important to the understanding of the observed properties of this system at low doping levels. Magnetic resonance techniques provide powerful experimental probes into the nature and environment of these neutral-radical defects. In an earlier work we showed that firstprinciples spin-polarized local density functional (LDF) methods reliably predict proton Fermi-contact coupling constants for planar, neutral, organic π-radicals. We have also used these methods to calculate the Fermi-contact proton coupling constants associated with the soliton defect in polyacetylene.Herein we compare the results of these earlier soliton calculations to results from recent electron-nuclear double-resonance (ENDOR) experiments. Our predicted ratio of the negative to positive spin densities is in good agreement with these ENDORstudies. The negative spin densities arise from spin-polarization effects which are found to cause the soliton level at midgap to be split by several tenths of an eV.

Type
Research Article
Copyright
Copyright © Materials Research Society 1991

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