Nanotube potentials

This page indexes some quick examples of how to calculate the potential difference between the inside and the outside of a nanotube using c2x and various DFT codes. The results are not of publishable quality: no convergence checking has been done. They are presented merely as a tutorial.

All use c2x's ability to roll sheets into nanotubes, and start from a graphene sheet of:

graphene.cell

%block LATTICE_CART
  2.4577810   0.0000000   0.0000000
  1.2288905   2.1284998   0.0000000
  0.0000000   0.0000000  24.0
%endblock LATTICE_CART

%block POSITIONS_FRAC
  C  0.333333333  0.333333333  0.500000000
  C  0.666666667  0.666666667  0.500000000
%endblock POSITIONS_FRAC

For this rather small radius nanotube, the rough answers are Abinit 0.75V, QE 0.63V, Castep 0.61V and Vasp 0.57V. All used different pseudopotentials, and no attempt was made to use identical, or converged, kpoint meshes, so no conclusions can validly be drawn from these numbers. The above figures are obtained from the differences between two points, whereas one ought to average as below.

C2x can also produce radial plots after averaging over the tube length and theta.

Three unit cells of nanotube