Carbon Nanotube

Chiral index n 10

Chiral index m 10

Tube length 14 rings

Diameter

0 nm

Chiral angle

0°

Conduction

–

Atoms shown

How it works

A single-wall carbon nanotube is a graphene honeycomb sheet rolled up so that one lattice point maps onto another. The vector connecting those two points is the chiral vector C_h = n·a₁ + m·a₂, and it fixes everything about the tube's geometry and electronics.

d = a·√(n²+nm+m²) / π      (diameter, a = 0.246 nm)
θ = atan[ √3·m / (2n+m) ]  (chiral angle, 0°–30°)
metallic  if (n−m) mod 3 = 0
semiconducting otherwise

n, m — chiral indices: n=m gives an "armchair" tube (always metallic), m=0 gives "zigzag", anything else is "chiral".
Tube length — number of hexagon rings modelled, extended live by CVD growth.
CVD growth — chemical vapour deposition: carbon feedstock decomposes on a catalyst particle and the tube lengthens one ring at a time, exactly as shown here.
Electron flow — toggles a stream of charge carriers along the tube axis, visible only when the (n−m) mod 3 = 0 metallic rule is satisfied in real nanotubes; here it always runs so you can see the transport path, but the readout tells you the true regime.

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