Calculation at Gamma Point (Hexagonal Cell)

[tyson]

Dear All:
I obtain the error message " VERY BAD NEWS! internal error in subroutine IBZKPT: Tetrahedron method fails for NKPT<4. NKPT = 1" when I try to run VASP for a large cell by calculating at the gamma point only. Please tell me how I can resolve it. The KPOINT file and POSCAR file are below.
T. A. Tyson


***************
KPOINTS

1 x 1 x 1 k-mesh (automatic generation of k-points)
0
Gamma
1 1 1
0 0 0

***********
POSCAR

120 atoms ,
1.00000000000000
12.2826 0.00000 0.00
-6.1413 10.637000 0.00000
0.00000 0.0000000 11.4122
24 72 24
Direct
0.161200 0.000000 0.000000
0.000000 0.161200 0.000000
0.338800 0.338800 0.000000
0.338800 0.000000 0.500000
0.000000 0.338800 0.500000
0.161200 0.161200 0.500000
.
.
>

[giacomo giorgi]

The answer is in the message you got. The sampling you use for this cell is too small....just one kpoint, while for ISMEAR=-5 (tetrahedron method) you need at least 4 kpoint.... try increasing the sampling since you get NKPT=4, or, according to the system you are studying, change ISMEAR to 0 or 1.

Best,
G

[tyson]

Thanks

TAT