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Posted: **Wed Jun 14, 2023 2:59 am**

Dear VASP team,

Recently, our research group found a strange behavior on the band structure calculated by PBE0 funcitonal (LHFCALC = .TRUE. and HFSCREEN = 0.0).
I attach several band structures calculated with VASP-6.4.2 with varying HFSCREEN =0.0 to 0.1.
We have seen the exactly same erroneous behavior with VASP-6.4.1.

bug-report-VASP64.png

Obviously, hybrid functional with small exchange screening seemingly cause significant error on the band structures and gradually rectified with increasing the HFSCREEN parameter.

Remarkably, we also confirmed that VASP-6.3.X version dose not exhibit this erroneous behavior.

Here I attach the POSCAR, INCAR, KPOINTS of bulk Si where I observe the erroneous band structure.

Code: Select all

Si2
1.0
0.0000000000 2.7333568822 2.7333568822
2.7333568822 0.0000000000 2.7333568822
2.7333568822 2.7333568822 0.0000000000
Si
2
direct
0.7500000000 -0.2500000000 0.7500000000 Si
0.5000000000 0.5000000000 -0.5000000000 Si

Code: Select all

ALGO  =  Normal

PREC   =  Normal
LREAL  =  False
LASPH  =  True
NELM   =  100

ISMEAR  =  0
SIGMA   =  0.1

LWAVE   =  False
LCHARG  =  False

NBANDS  =  12
LORBIT  =  10

# hybrid functional
LHFCALC = .TRUE.
GGA = PE

# parallel
KPAR  =  4
NCORE =  4

Code: Select all

0.040   8   8   8   29  0.060   83    6   19    6   20   16   13    9           # Parameters to Generate KPOINTS (Do NOT Edit This Line)
   112
Reciprocal lattice
    0.00000000000000    0.00000000000000    0.00000000000000     1
    0.12500000000000    0.00000000000000    0.00000000000000     8
    0.25000000000000    0.00000000000000    0.00000000000000     8
    0.37500000000000    0.00000000000000    0.00000000000000     8
    0.50000000000000    0.00000000000000    0.00000000000000     4
    0.12500000000000    0.12500000000000    0.00000000000000     6
    0.25000000000000    0.12500000000000    0.00000000000000    24
    0.37500000000000    0.12500000000000    0.00000000000000    24
    0.50000000000000    0.12500000000000    0.00000000000000    24
   -0.37500000000000    0.12500000000000    0.00000000000000    24
   -0.25000000000000    0.12500000000000    0.00000000000000    24
   -0.12500000000000    0.12500000000000    0.00000000000000    12
    0.25000000000000    0.25000000000000    0.00000000000000     6
    0.37500000000000    0.25000000000000    0.00000000000000    24
    0.50000000000000    0.25000000000000    0.00000000000000    24
   -0.37500000000000    0.25000000000000    0.00000000000000    24
   -0.25000000000000    0.25000000000000    0.00000000000000    12
    0.37500000000000    0.37500000000000    0.00000000000000     6
    0.50000000000000    0.37500000000000    0.00000000000000    24
   -0.37500000000000    0.37500000000000    0.00000000000000    12
    0.50000000000000    0.50000000000000    0.00000000000000     3
    0.37500000000000    0.25000000000000    0.12500000000000    24
    0.50000000000000    0.25000000000000    0.12500000000000    48
   -0.37500000000000    0.25000000000000    0.12500000000000    24
    0.50000000000000    0.37500000000000    0.12500000000000    24
   -0.37500000000000    0.37500000000000    0.12500000000000    48
   -0.25000000000000    0.37500000000000    0.12500000000000    24
   -0.37500000000000    0.50000000000000    0.12500000000000    12
   -0.25000000000000    0.50000000000000    0.25000000000000     6
    0.00000000000000    0.00000000000000    0.00000000000000     0
    0.02777777777778    0.00000000000000    0.02777777777778     0
    0.05555555555556    0.00000000000000    0.05555555555556     0
    0.08333333333333    0.00000000000000    0.08333333333333     0
    0.11111111111111    0.00000000000000    0.11111111111111     0
    0.13888888888889    0.00000000000000    0.13888888888889     0
    0.16666666666667    0.00000000000000    0.16666666666667     0
    0.19444444444444    0.00000000000000    0.19444444444444     0
    0.22222222222222    0.00000000000000    0.22222222222222     0
    0.25000000000000    0.00000000000000    0.25000000000000     0
    0.27777777777778    0.00000000000000    0.27777777777778     0
    0.30555555555556    0.00000000000000    0.30555555555556     0
    0.33333333333333    0.00000000000000    0.33333333333333     0
    0.36111111111111    0.00000000000000    0.36111111111111     0
    0.38888888888889    0.00000000000000    0.38888888888889     0
    0.41666666666667    0.00000000000000    0.41666666666667     0
    0.44444444444444    0.00000000000000    0.44444444444444     0
    0.47222222222222    0.00000000000000    0.47222222222222     0
    0.50000000000000    0.00000000000000    0.50000000000000     0
    0.50000000000000    0.00000000000000    0.50000000000000     0
    0.52500000000000    0.05000000000000    0.52500000000000     0
    0.55000000000000    0.10000000000000    0.55000000000000     0
    0.57500000000000    0.15000000000000    0.57500000000000     0
    0.60000000000000    0.20000000000000    0.60000000000000     0
    0.62500000000000    0.25000000000000    0.62500000000000     0
    0.37500000000000    0.37500000000000    0.75000000000000     0
    0.35526315789474    0.35526315789474    0.71052631578947     0
    0.33552631578947    0.33552631578947    0.67105263157895     0
    0.31578947368421    0.31578947368421    0.63157894736842     0
    0.29605263157895    0.29605263157895    0.59210526315789     0
    0.27631578947368    0.27631578947368    0.55263157894737     0
    0.25657894736842    0.25657894736842    0.51315789473684     0
    0.23684210526316    0.23684210526316    0.47368421052632     0
    0.21710526315789    0.21710526315789    0.43421052631579     0
    0.19736842105263    0.19736842105263    0.39473684210526     0
    0.17763157894737    0.17763157894737    0.35526315789474     0
    0.15789473684211    0.15789473684211    0.31578947368421     0
    0.13815789473684    0.13815789473684    0.27631578947368     0
    0.11842105263158    0.11842105263158    0.23684210526316     0
    0.09868421052632    0.09868421052632    0.19736842105263     0
    0.07894736842105    0.07894736842105    0.15789473684211     0
    0.05921052631579    0.05921052631579    0.11842105263158     0
    0.03947368421053    0.03947368421053    0.07894736842105     0
    0.01973684210526    0.01973684210526    0.03947368421053     0
    0.00000000000000    0.00000000000000    0.00000000000000     0
    0.00000000000000    0.00000000000000    0.00000000000000     0
    0.03333333333333    0.03333333333333    0.03333333333333     0
    0.06666666666667    0.06666666666667    0.06666666666667     0
    0.10000000000000    0.10000000000000    0.10000000000000     0
    0.13333333333333    0.13333333333333    0.13333333333333     0
    0.16666666666667    0.16666666666667    0.16666666666667     0
    0.20000000000000    0.20000000000000    0.20000000000000     0
    0.23333333333333    0.23333333333333    0.23333333333333     0
    0.26666666666667    0.26666666666667    0.26666666666667     0
    0.30000000000000    0.30000000000000    0.30000000000000     0
    0.33333333333333    0.33333333333333    0.33333333333333     0
    0.36666666666667    0.36666666666667    0.36666666666667     0
    0.40000000000000    0.40000000000000    0.40000000000000     0
    0.43333333333333    0.43333333333333    0.43333333333333     0
    0.46666666666667    0.46666666666667    0.46666666666667     0
    0.50000000000000    0.50000000000000    0.50000000000000     0
    0.50000000000000    0.50000000000000    0.50000000000000     0
    0.50000000000000    0.47916666666667    0.52083333333333     0
    0.50000000000000    0.45833333333333    0.54166666666667     0
    0.50000000000000    0.43750000000000    0.56250000000000     0
    0.50000000000000    0.41666666666667    0.58333333333333     0
    0.50000000000000    0.39583333333333    0.60416666666667     0
    0.50000000000000    0.37500000000000    0.62500000000000     0
    0.50000000000000    0.35416666666667    0.64583333333333     0
    0.50000000000000    0.33333333333333    0.66666666666667     0
    0.50000000000000    0.31250000000000    0.68750000000000     0
    0.50000000000000    0.29166666666667    0.70833333333333     0
    0.50000000000000    0.27083333333333    0.72916666666667     0
    0.50000000000000    0.25000000000000    0.75000000000000     0
    0.50000000000000    0.25000000000000    0.75000000000000     0
    0.50000000000000    0.21875000000000    0.71875000000000     0
    0.50000000000000    0.18750000000000    0.68750000000000     0
    0.50000000000000    0.15625000000000    0.65625000000000     0
    0.50000000000000    0.12500000000000    0.62500000000000     0
    0.50000000000000    0.09375000000000    0.59375000000000     0
    0.50000000000000    0.06250000000000    0.56250000000000     0
    0.50000000000000    0.03125000000000    0.53125000000000     0
    0.50000000000000    0.00000000000000    0.50000000000000     0

We note that the band structures are obtained with the conventional zero-weight K-points for the hybrid functional calculation.

Thank you in advance,

SB

Posted: **Thu Jun 15, 2023 11:01 am**

Hi,

Yes, this looks worrisome. We will investigate the issue and let you know as soon as possible.

Marie-Therese

Posted: **Thu Jun 15, 2023 12:51 pm**

Hi,

In short, the solution is to set HFRCUT=-1.

On a regular grid, VASP uses auxiliary functions (HFALPHA) for the coulomb truncation of the bare coulomb by default. This method is not supported for band-structure calculations. Instead, the coulomb truncation (HFRCUT) works well in that case, but it must be set explicitly. Then, there are no discontinuities in the band structures. You can also read more here: Coulomb_singularity and HFALPHA.

It is a bit confusing what you say about the different VASP versions. I see the same behavior in VASP 6.3.x and VASP 6.4.x. Perhaps you have changed the k-point sampling and accidentally avoided the problem

Furthermore, thus far, we have released 6.4.0 and 6.4.1. VASP 6.4.2 does not exist.

Does that solve your issue?

Best,
Marie-Therese

Posted: **Wed Jun 21, 2023 3:20 am**

Dear VASP team,

I inform you that the problem related to wiggling eigenvalues in PBE0 calculated band structure has been resolved with HFRCUT= -1.

Thank you for your support!

SB

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