Result different for different K mesh and different between self consistent and non self consistent

[hatdau]

Hi I am calculating with two k-mesh:
Monkhorst pack: 12 12 12
and : 41 41 41
using VASP 4.6.36 with same setting in INCAR:
PREC=NORMAL
ENCUT=400
ISMEAR=-5

I got different band gap:
12 12 12: -0.070 eV(pseudo gap)
41 41 41: -0.16 eV
That's huge difference.

How every if I do non self-consistent with kmesh of 41x41x41 from scf for both cases with setting:
ICHARG=11
ISTART=1
I Got got similar result:
12 12 12 -> 41 41 41: -0.086eV
41 41 41 -> 41 41 41: -0.084eV

Any idea how that happens?

Thanks

[hatdau]

Just give you more information:

The problem were Gamma point. The difference between self-consistent and non self-consistent occurred when the Gamma point was included.

And also when included Gamma point the self consistent results are different from those with out Gamma point.

Hope someone can have suggestions on this.
<span class='smallblacktext'>[ Edited Tue Jul 13 2010, 05:56PM ]</span>