Diameter dependent wall deformations during the compression of a carbon nanotube bundle

Abstract

Raman scattering is used to study the pressure-dependence of the radial (R) bands of bundled single-walled carbon nanotubes (SWNT) produced by the HiPCO process. We find that the normalized pressure derivative of the R-band frequency, $\ensuremath{\Phi}=d(\mathrm{ln}{\ensuremath{\omega}}_{\mathrm{R}})/dP,$ increases with increasing nanotube diameter D as $\ensuremath{\Phi}\ensuremath{\sim}{D}^{2}.$ Using results from elastic theory, we show that the contribution to \ensuremath{\Phi} from isolated SWNT, $(={\ensuremath{\Phi}}_{0}),$ is small, which agrees with previous model calculations. We show here that ${\ensuremath{\Phi}}_{0}$ is independent of D. We conclude that most of the pressure dependence observed for the R bands in SWNT bundles may be identified with tube wall deformations mediated via tube-tube interactions within a bundle and not with the compression of an individual tube.