25,437 research outputs found
A Amazônia e os desafios de sua ocupação.
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Características da agricultura indígena e sua influência na produção familiar da Amazônia.
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Polarons in Carbon Nanotubes
Full text linkWe use ab initio total-energy calculations to predict the existence of
polarons in semiconducting carbon nanotubes (CNTs). We find that the CNTs' band
edge energies vary linearly and the elastic energy increases quadratically with
both radial and with axial distortions, leading to the spontaneous formation of
polarons. Using a continuum model parametrized by the ab initio calculations,
we estimate electron and hole polaron lengths, energies and effective masses
and analyze their complex dependence on CNT geometry. Implications of polaron
effects on recently observed electro- and opto-mechanical behavior of CNTs are
discussed.Comment: Revtex preprint format, 12 pages, 2 eps figures, source in LaTeX.
Accepted for publication in Physical Review Letter
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