Enhancement factor of open thick-wall carbon nanotubes

We have calculated the electric field around and on the surface of an open thick-wall carbon nanotube (CNT) of height h, external radius R, and wall thickness w. To accomplish that we simulate the CNT as a vertical array of touching toroids, each of external radius R and cross section radius w/2, and then we express the problem in toroidal coordinates. From our calculations we obtain the enhancement factor gamma as a function of h, R, and w. By fitting to our numerical results we obtain an empirical but simple formula for gamma, which extrapolates to that of a closed CNT in the limiting case of w=R. (C) 2004 American Institute of Physics.