Pressure-induced phase transformation and structural resilience of single-wall carbon nanotube bundles

We report here an in situ x-ray diffraction investigation of the structural changes in carbon single-wall nanotube bundles under quasihydrostatic pressures up to 13 GPa. In contrast with a recent study [Phys. Rev. Lett. 85, 1887 (2000)] our results show that the triangular lattice of the carbon nanotube bundles continues to persist up to \ensuremath{\sim}10 GPa. The lattice is seen to relax just before the phase transformation that is observed at \ensuremath{\sim}10 GPa. Further, our results display the reversibility of the two-dimensional lattice symmetry even after compression up to 13 GPa well beyond the 5 GPa value observed recently. These experimental results explicitly validate the predicted remarkable mechanical resilience of the nanotubes.