Open Access

ARTICLE

Bonding Geometry and Bandgap Changes of Carbon Nanotubes Under Uniaxial and Torsional Strain

Liu Yang¹, Jie Han, M. P. Anantram, Richard L. Jaffe

1 liuyang@pegasus.arc.nasa.gov, NASA Ames Research Center, Mail Stop 230, Moffett Field, CA 94035

Computer Modeling in Engineering & Sciences 2002, 3(5), 675-686. https://doi.org/10.3970/cmes.2002.003.675

Abstract

Bonding geometry and bandgap of carbon nantotubes under uniaxial and torsional deformation are studied computationally for nanotubes of various chiralities and diameters. Bonding geometries are obtained with Tersoff-Brenner potential from molecular mechanics simulations. Bandgaps as function of strain are calculated from the molecular mechanics structures using one (p) and four (2s and 2p_x, 2p_y, 2p_z) orbital tight-binding models. For small strains, the bandgap results are qualitatively consistent with those predicted by the one orbital analytical model. Response of the electronic properties of nanotubes to large strains is characterized by a change in sign of d(bandgap)/d(strain). These originate from either quantum number or bonding geometry effects, and are strain-induced semiconductor-metal transitions. The effect of variations in bonding geometries between continuum mechanics and molecular mechanics structures on the electronic properties and differences between the one and four orbital models are also presented.

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