16
$\begingroup$

I performed an HSE06 calculations using VASP and the calculated band gap is in good agreement with experiment. However the band is not smooth, with very sharp, zig-zag like features. How to improve the smoothness of the band structure?

$\endgroup$
3
  • 1
    $\begingroup$ I think that you need to change the number of k-points you are using in your path between the high symmetry points at the Brillouin zone. $\endgroup$ – Camps May 18 '20 at 11:50
  • $\begingroup$ User CKI asks (but doesn't have enough rep to write a comment): "Could you post the KPOINTS file? I suspect that you eventually do not use an actual path." $\endgroup$ – Nike Dattani May 24 '20 at 17:47
  • $\begingroup$ Adding to what I.Camps said, your problem is either: i) The plane wave cutoff - You need to test convergence with respect to this. If you want to avoid the convergence test, you can take 1.3*Emax in VASP, which is what is recommended. ii) K-point grid - There is no work-around to testing convergence wrt this. There are some general guidelines(use even no. of K points etc).. iii) Smearing: If your material has a gap more than say 0.2-0.3 eV, then you don't need to worry about this. Finally, your method of generating band structures can also be at the heart of the problem - How did you do it? $\endgroup$ – Xivi76 Jun 13 '20 at 18:47
5
$\begingroup$

Normally, this could happen due to several issues:

  • discontinuity in the k-path you selected to calculate the band structure,
  • low number of points in each interval,
  • bad convergence parameters.
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.