A theoretical, stable, helical nanotube structure, which is analogous to that seen in crystal growth affected by screw dislocations.

The structure is composed of 5, 6 and 7 membered-rings. Carbon rings with 5 members are shown in red, 6 in grey and seven in yellow.

There is a passing resemblance to the spiral structure of DNA (but a single helix, obviously).

Also referred to as "helicoidal graphite"