Figure 2.

Geometry of (6, 6) CNC from side view (left plot) and top view (right plot); the latter is a hexagonal nanotori. a is the side length of hexagon, D is the diameter of the inner ring. The area of cross section (from top view) is computed by

Liu et al. Nanoscale Research Letters 2010 5:478-483   doi:10.1007/s11671-010-9545-x