Hi,

I have a question about the values of the nanotube diameter and circumference reported in the output log.

For example, an (8, 0) zig-zag nanotube is reported to have a diameter of 0.62631 nm and a circumference of 8 nm.

Since a cross-sectional view down the axis of a CNT appears to be circular, should the diameter and circumference be related by the geometrical equation:

circumference = pi * diameter ?

That is clearly not the case for this example, where circumference = 12.77 * diameter.

This ratio of circumference / diameter is close to 4 * pi, and the same ratio exists for 13 other (n,m) values that I tried.  

Is there something I am missing, or there is a glitch in the calculation?   

Thank you for looking into this.

Tanya