Tetrahedron method with small number of kpts

[andrew_rosen]

I am running a tetrahedron calculation with a 2x2x2 Monkhorst-Pack k-point grid and get the following error. Is this expected given that there are 8 k-points total? I am using VASP 6.4.1.

Code: Select all

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|                                                                             |
|     EEEEEEE  RRRRRR   RRRRRR   OOOOOOO  RRRRRR      ###     ###     ###     |
|     E        R     R  R     R  O     O  R     R     ###     ###     ###     |
|     E        R     R  R     R  O     O  R     R     ###     ###     ###     |
|     EEEEE    RRRRRR   RRRRRR   O     O  RRRRRR       #       #       #      |
|     E        R   R    R   R    O     O  R   R                               |
|     E        R    R   R    R   O     O  R    R      ###     ###     ###     |
|     EEEEEEE  R     R  R     R  OOOOOOO  R     R     ###     ###     ###     |
|                                                                             |
|     VERY BAD NEWS! internal error in subroutine BZINTS: Tetrahedron         |
|     method fails (number of k-points < 4) 2                                 |
|                                                                             |
|       ---->  I REFUSE TO CONTINUE WITH THIS SICK JOB ... BYE!!! <----       |
|                                                                             |
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Reproduction:

INCAR:
ENCUT = 520.000000
SIGMA = 0.050000
EDIFF = 1.00e-05
ALGO = fast
GGA = PE
PREC = accurate
EFERMI = midgap
ISMEAR = -5
LORBIT = 11
NELM = 150
NELMIN = 3
NSW = 0
IVDW = 12
NEDOS = 5001
LAECHG = .TRUE.
LASPH = .TRUE.
LCHARG = .TRUE.
LWAVE = .TRUE.
LREAL = .FALSE.

KPOINTS:
KPOINTS created by Atomic Simulation Environment
0
Monkhorst-Pack
2 2 2
0 0 0

POSCAR:
C
1.0000000000000000
0.0000000128040216 1.7791658639596684 1.7791658639625925
1.7791658639527810 0.0000000128159660 1.7791658639597869
1.7791658639359635 1.7791658639770385 0.0000000127864157
C
2
Cartesian
-0.0000000069344735 -0.0000000069322343 -0.0000000058567941
0.8895829421076652 0.8895829421204026 0.8895829410339929

POTCAR:
PAW_PBE for C

MS: Made the error message more readable.

[martin.schlipf]

Currently, VASP only checks the absolute number of k points. Your k-point mesh generates only 2 irreducible k points. As you stated, this choice is in principle to conservative. If the underlying mesh has more k points, it should be fine to use it to generate tetrahedra. I would need to test carefully whether this runs into any other issues, though.