Wrong stress tensor computed by VASP 4.6?

[maartendft]

POSCAR for FCC aluminium, strain applied in c-directionj:

mode3_2
1.00000000
4.046202342817 0.000000000000 0.000000000000
0.000000000000 4.046202342817 0.000000000000
0.000000000000 0.000000000000 4.066664366245
4
Direct
0.000000000000 0.500000000000 0.000000000000
0.500000000000 0.000000000000 0.500000000000
0.500000000000 0.000000000000 0.000000000000
0.000000000000 0.500000000000 0.500000000000

When I run VASP with ISIF=2 and 20*20*20 k-point grid, ENCUT 700 eV, ISMEAR=2 and the other setting all on the safe side, I find a stress tensor in the OUTCAR as follows:

Total 0.35 0.35 55.31 0.00 0.00 0.00
in kB 8.39 8.39 1330.94 0.00 0.00 0.00
external pressure = 449.24 kB Pullay stress = 0.00 kB

I.e. much too high stress in c-direction! Does anyone have any ideas what went wrong?

Many thanks,

Maarten

[forsdan]

Your given positions don't represent a fcc cell. Try to repeat it with the following direct coordinates:

0.0000000000000000 0.0000000000000000 0.0000000000000000
0.5000000000000000 0.0000000000000000 0.5000000000000000
0.5000000000000000 0.5000000000000000 0.0000000000000000
0.0000000000000000 0.5000000000000000 0.5000000000000000

Best regards,
/Dan
<span class='smallblacktext'>[ Edited Sun Jun 06 2010, 10:11PM ]</span>