vasp error:Reciprocal lattice and k-lattice belong to different class of lattices

[fangzhu]

Dear all,
I am a newer for vasp. I recently calculated (vasp4.6) a body-centered superlattice using premitive cell (4 atoms). Then the error occured:Reciprocal lattice and k-lattice belong to different class of lattices. But calculation went on and converged. I am not sure the result is reliable or not. I turned to unit cell with 8 atoms, calculation is OK. I searched the former relavant threads but they did not help. The following are my input files

POSCAR
NMG
5.8200
-0.353553390593274 0.353553390593274 0.500000000000000
0.353553390593274 -0.353553390593274 0.500000000000000
0.353553390593274 0.353553390593274 -0.500000000000000
1 1 2
Direct
0.0000000000000000 0.0000000000000000 0.0000000000000000
0.5000000000000000 0.5000000000000000 0.0000000000000000
0.2500000000000000 0.7500000000000000 0.5000000000000000
0.7500000000000000 0.2500000000000000 0.5000000000000000

KPOINTS
Automatic
0
Auto
50
0 0 0

INCAR
Start parameter for the Run:
ISTART = 0
ICHARG = 2
INIWAV = 1

Electronic Relaxation
PREC = Accurate
ENCUT = 350 eV
GGA = PE
ISPIN = 2
NBANDS = 72
IALGO = 38
NELM = 60; NELMIN= 0; NELMDL= 3
EDIFF = 1E-07
AMIX = 0.2
BMIX = 0.5
ISYM = 2
TIME = 0.05
LORBIT = 11
VOSKOWN= 1
MAGMOM = 1*4 1*-0.1 2*0.1

Geometric Relaxation
ISIF = 3
EDIFFG = -1E-05
NSW = 70
IBRION = 1
POTIM = 0.20

Others
LREAL = .FALSE.
LWAVE=.FALSE.
LCHARG=.TRUE.

DOS related values:
ISMEAR = 1 ; SIGMA = 0.1
EMIN = -5 ; EMAX = 15

It is curious that the k-mesh generation method used in the KPOINTS makes a 15 15 17 grid (from OUTCAR). Yet the c-axis is longer than a or b axis. So what is wrong? I did have tried the Monkhorst-Pack scheme for k-mesh generation but got the same errors. Any idea is greatly appreciated. Thank you in advance!

FZ

[boris]

Hi

Your KPOINT file seems strange to me. Why don't you use a standard Monkhorst-Pack generation scheme? That should look like this:

Automatic
0
Monkhorst-Pack
7 7 7
0 0 0

Of course, you can use other values than 7x7x7.

Boris

[fangzhu]

[quote="boris"]Hi

Your KPOINT file seems strange to me. Why don't you use a standard Monkhorst-Pack generation scheme? That should look like this:

Automatic
0
Monkhorst-Pack
7 7 7
0 0 0

Of course, you can use other values than 7x7x7.

Boris[/quote]
Thank you for your reply. This is the fully automatic scheme which generates gamma centered Monkhorst-Pack grids. I just have tried the Monkhort-pack scheme with 9 9 9, it seems working. Well, I feel confused why the fully automatic scheme gives an error since it can be treated as giving same density of K points along the three reciprocal primitive vectors.