Compressibility and Polygonization of Single-Walled Carbon Nanotubes under Hydrostatic Pressure

TLDR: Theoretical calculations suggest that single-walled carbon nanotubes are polygonized when they form bundles of hexagonal close-packed structure and the intertubular gap is smaller than the equilibrium spacing of graphite.

Abstract: Single-walled carbon nanotubes show linear elasticity under hydrostatic pressure up to 1.5 GPa at room temperature. The volume compressibility, measured by in situ synchrotron x-ray diffraction, has been determined to be $0.024\mathrm{GPa}{}^{\ensuremath{-}1}$. Theoretical calculations suggest that single-walled carbon nanotubes are polygonized when they form bundles of hexagonal close-packed structure and the intertubular gap is smaller than the equilibrium spacing of graphite (002) $(d\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3.35\phantom{\rule{0ex}{0ex}}\AA{})$. It has also been determined that the deformation of the trigonal nanotube lattice under hydrostatic pressure is reversible up to 4 GPa, beyond which the nanotube lattice is destroyed.