5
$\begingroup$

I am using HSE06 hybrid functional to calculate the band structure. I copied IBZKPT file as the KPOINTS file and pasted the k point path for the band structure after this file. The k point path for the band structure was obtained by another band structure calculation with PBE functional for the same system before. The new KPOINTS files is shown below.

Automatically generated mesh
61
Reciprocal lattice
0.00000000000000 0.00000000000000 0.00000000000000 1
0.09090909090909 0.00000000000000 0.00000000000000 2
...
-0.09090909090909 0.45454545454546 0.00000000000000 2
0.00000000 0.00000000 0.00000000 0.000
...
0.50000000 0.50000000 0.00000000 0.000

The INCAR file is shown below.

ISTART = 1
LWAVE = .FALSE.
LCHARGE = .TRUE.
ICHARG = 11
IVDW = 12
ISPIN = 2
MAGMOM = 0.156 -0.155 -0.096 0.096 -0.156 0.155 -0.156 0.155 0.096\
-0.096 0.156 -0.155 -0.156 0.155 0.096 -0.096 0.156 -0.155\
0.156 -0.155 -0.096 0.096 -0.156 0.155
LORBIT = 11
ENCUT = 500
ISMEAR = 0
SIGMA = 0.03
PREC = Accurate
LHFCALC = .TRUE.
AEXX = 0.25
HFSCREEN = 0.2
ALGO = Damped
TIME = 0.4
PRECFOCK = Fast
ISYM = 3
LREAL = Auto
NELMIN = 5
NELM = 700
NELMDL = -10
EDIFF = 1e-5
NPAR = 32
KPAR= 16

After the NSCF calculation done, the band structure is completely wrong. I upload the band structure below, which I obtained through using p4v software to read vasprun.xml file from the non-self consistent calculation with the HSE06 hybrid functional.

enter image description here

The output file shows the warning information below.

| |
| W W AA RRRRR N N II N N GGGG !!! |
| W W A A R R NN N II NN N G G !!! |
| W W A A R R N N N II N N N G !!! |
| W WW W AAAAAA RRRRR N N N II N N N G GGG ! |
| WW WW A A R R N NN II N NN G G |
| W W A A R R N N II N N GGGG !!! |
| |
| Your generating k-point grid is not commensurate to the symmetry |
| of the lattice. This can cause slow convergence with respect |
| to k-points for HF type calculations |
| suggested SOLUTIONS: |
| ) if not already the case, use automatic k-point generation |
| ) shift your grid to Gamma (G) (e.g. required for hex or fcc lattice) |
| |
-----------------------------------------------------------------------------

I am doing the band structure calculation and I have to set up the k point path manually. I cannot use automatic k-point generation, which is used in single point calculation so I do not understand what VASP means by use automatic k-point generation in this band structure calculation step.

Would anyone please give me some suggestions on the solution?

Thank you very much.

Kieran

$\endgroup$
2
  • 1
    $\begingroup$ Can you explain what do you mean by "completely wrong"? $\endgroup$ Commented Sep 26, 2021 at 9:35
  • $\begingroup$ It seems you may have accidentally made a second account. If you want to merge these, follow the instructions from the help page: mattermodeling.stackexchange.com/help/merging-accounts $\endgroup$
    – Tyberius
    Commented Sep 27, 2021 at 3:02

2 Answers 2

5
$\begingroup$

As the error indicate:

| Your generating k-point grid is not commensurate to the symmetry |
| of the lattice. This can cause slow convergence with respect |
| to k-points for HF type calculations |
| suggested SOLUTIONS: |
| ) if not already the case, use automatic k-point generation |
| ) shift your grid to Gamma (G) (e.g. required for hex or fcc lattice) |

You need to define/use a correct k-point path.

As you already state that you can not use automatic k-point generation, the solution is:

  • Identify the crystal symmetry you are working on.
  • Look for the Brillouin zones of that symmetry.
  • Select the high symmetry points for the path.
  • Generate the k-point between each symmetry points.

Take o look here about how to accomplish these tasks.

$\endgroup$
3
  • $\begingroup$ Thank you for the suggestion. Previously, I did the band structure calculation for this same crystal system with the PBE functional through the VASP code. In that previous band structure calculation, I used high-symmetry k point and the calculation was done successfully. After that, I re-did this calculation with the HSE06 hybrid functional and I used the high-symmetry k point, which I used in the previous calculation with PBE functional. I do not understand why the high-symmetry k point does not work in the calculation with HSE06 hybrid functional... $\endgroup$
    – Kieran
    Commented Sep 27, 2021 at 14:43
  • $\begingroup$ ...while works in the calculation with PBE functional. Would you please give me more suggestions on the solution? (Reproduced from Kieran's comment since it got too long). $\endgroup$
    – Tyberius
    Commented Sep 27, 2021 at 16:44
  • $\begingroup$ I really don't know expect such behavior. My only recommendation is to use a clean folder with the input files only and run the calculation again. $\endgroup$
    – Camps
    Commented Sep 27, 2021 at 23:10
4
$\begingroup$

This is an older question, but I faced something similar. Not sure if what I'm about to say applies to this case, but it might be a useful to have a record of this as a possible thing to troubleshoot for, for anybody who stumbles upon this post with similar issues.

Having followed similar steps as OP and got a similarly strange looking band structure, I found out my mistake was that I did not change the number of k-points on the second line of the KPOINTS file (it was left as the original number in the IBZKPT file). It should have been that value plus the number of zero-weighted k-points in the band structure path that was appended to the renamed IBZKPT->KPOINTS file. What my band structure plot showed was a 'k-path' through a uniform k-point mesh rather than through the desired high-symmetry k-point path.

I noticed my mistake upon a closer look at

  1. VASP Wiki's KPOINTS page, under "Explicit k-point mesh" where it specifies "Provide the number of k points on the second line."
  2. VASP Wiki's HSE band structure tutorial, in the KPOINTS file under "Procedure 2: 0-weight (Fake) SC procedure (PBE & Hybrids)", where they explicitly put the number of k-points as the number of weighted k-points that form a mesh, and the zero-weighted k-points on the high-symmetry path for band structure plotting. (The IBZKPT file from a previous regular-meshed k-point calculation only has the number of mesh k-points in its second line)
$\endgroup$

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .