[ase-users] band structure of carbon nanotubes

[Ask Hjorth Larsen]

Dear Ojha,

Jakob already mentioned most issues, but also, you need to make sure you
have an actual 1D bandpath.  Like cell.bandpath(..., pbc=[True, False,
False)).  Otherwise you will be sampling a 3D Brillouin zone.

In general, don't write a long script and assume every (or any) step
works.  Do one thing, check it, fix it until you see that it is correct,
then do one more thing.  It's the only way.

Best regards
Ask

Am Mi., 4. Sept. 2024 um 11:58 Uhr schrieb Dr. Ojha Deepak via ase-users <
ase-users at listserv.fysik.dtu.dk>:

> Dear ASE/GPAW users,
> I would like to calculate the band structure of carbon nanotubes of
> chirality like (6,2), (6,4) and (6,6) using ASE/GPAW. I have a doubt about
> the structure of carbon nanotube being properly replicated in z-axis as
> built using ASE.  My python script is given below:
>
> ----------------------------------------------------------------------------------------------------------
> from gpaw import GPAW, PW
> from ase import Atoms
> from ase.build import nanotube
> from ase.cell import Cell
> from ase.visualize import view
> from ase.io import read, write;
> atoms1 = nanotube(6, 6, length=4)
> atoms1.cell = Cell.fromcellpar([4, 4, 4, 90, 90, 90])
> atoms1.set_pbc((True, True, True))
> write('66cnt.traj', atoms1)
> write('cnt.xyz',read('66cnt.traj'))
> calc = GPAW(mode=PW(800), kpts=[8, 8, 8], xc='revPBE',
>              txt='gpaw.cnt1.txt')
> atoms1.calc = calc
>
> atoms1.get_potential_energy()
> calc.write('66cnt.gpw')
>
> path = atoms1.cell.bandpath(density=7)
> path.write('path.66cnt.json')
> print('path')
> calc = calc.fixed_density(kpts=path, symmetry='off')
>
> bs = calc.band_structure()
> bs.write('bs.66cnt.json')
>
> -----------------------------------------------------------------------------------------------------------------------------------
>
> Apart from it, the length=4 is probably not Angstroms or nanometers. In
> that
> case how do i define hte cell for my nanotube. I am not certain if the
> script is absolutely correct, so for any other suggestion, I will be
> highly
> obliged.
>
> Thanks and Best Regards,
> Deepak
>
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