ABSTRACT
Figure 1 shows the lattice structure and the first Brillouin zone of a two-dimensional (2D) graphite together with the coordinate systems. The unit cell contains two carbon atoms denoted
byAandB. A nanotube is specified by achiral vector L = naa+ribb with integer na and/tj, and basis vectors a and b (|a| = |b| = a = 2.46 A). In the coordinate system fixed onto a graphite sheet, we have a = (a, 0) and b = {—a /2, y/3a/2). For convenience we introduce another coordinate system where the x direction is along the circumference L and the y direction is along the axis of CN. The direction of L is denoted by the chiral angle rj.
