Carbon nanotubes specifying single wall

Let us fix the parameter 2A = 0.34 nm which is equal to the graphite inter-layer separation. The chirality and the radius of single-wall carbon nanotube are uniquely specified by the chiral vector C/, = iai +112 2 - ( i. 2)> where ni,ri2 are integers and ai, a2 are the unit cell basis vectors of graphite [1]. The chiral vector C is a circumferential lattice vector defined on nanotube surface, and C is perpendicular to the tube axis. For armchair nanotubes n =ri2 = n, and the tube radius r is defined by r = C/, /2ti = a f3n/2n, where a = 0.249 nm is the lattice constant for graphite. These values of r are used in our calculations. 

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