Nanotube in Abinit

To make a suitable .in file from the graphene sheet,

$ c2x -y=7,0 -v --abinit graphene.cell tube.in

The ecut parameter was changed to "450 eV" and the lines

prtvclmb 2
prtvha 1

appended to the file. A tube.files file was created containing

tube.in
tube.out
none
tube
tmp
C.psp8

and a pseudopotenial supplied by gunzipping C.psp8.gz.

Then Abinit was run:

$ abinit < tube.files > tube.log

The run took about four minutes, mostly due to the use of a rather unoptimised build of Abinit.

The potential far from the tube (i.e. at (0,0,0)) and at the centre of the tube (i.e. at (0.5,0.5,0.5)) can then be recovered as:

$ c2x -z='(0,0,0)'  tube_VCLMB
Potential_VCLMB at (0.000000,0.000000,0.000000): 3.927966e+00
$ c2x -z='(0.5,0.5,0.5)'  tube_VCLMB
Potential_VCLMB at (0.500000,0.500000,0.500000): 3.169207e+00

So a potential difference of about 0.759V. One can also ask c2x to calculate the potential from the charge density:

$ c2x -E -z='(0,0,0)'  tube_DEN
Potential_Volts at (0.000000,0.000000,0.000000): -3.941573e+00
$ /c2x -E -z='(0.5,0.5,0.5)'  tube_DEN
Potential_Volts at (0.500000,0.500000,0.500000): -3.187123e+00

Now a difference of 0.754V.