13.26 ps
14.08 ps
C68 cage
Self-capping in as short as 14.22 ps!
(1 4-ring, 12 5-rings, 17 6-rings and  4 7-rings)
The other end closes to 5/6/5 ring
DFTB/MD on SWNT with QM potential:
(5,5) 7.5 Å, 3000 K (III)
S. Irle, G. Zheng, M. Elstner, K. Morokuma, Nano Lett. 3(4), 465 (2003)
G. Zheng, S. Irle, M. Elstner, K. Morokuma,  J. Phys. Chem. A 108, 3182 (2004)