Precise determination of the threshold diameter for a single-walled carbon nanotube to collapse.

Closed-edged bilayer graphene nanoribbons were formed by the spontaneous collapse of large-diameter single-walled carbon nanotubes (SWNTs) grown on gold nanoparticles by chemical vapor deposition. Such bilayer graphene nanoribbons could adopt different stacking configurations, such as AB-stacking or stacking order with any rotation angle, correlated with the chiral angles of their parent rounded SWNTs. On the basis of the electron diffraction characterizations on a good number of collapsed and uncollapsed SWNTs, the threshold diameter for SWNTs to collapse was precisely determined to be 5.1 nm, independent of the chiral angle of the SWNTs. The determination is consistent with that calculated by both classical adaptive intermolecular reactive empirical bond order force field and density functional theory after having taken the stacking effect and thermal fluctuation into account.