DOS and band in Si slab model

[yzhu]

Dear everyone:

Why the dos of stable Si in slab model with surface has no gap? So the energy band with buckling dimer on surface shows metal nature . Thank you

INCAR
System = Si fcc
ISMEAR=0
#RWIGS=1.18
SIGMA=0.10
ENCUT=270 eV
IBRION=2
NSW=100
IALGO=48
ISTART=0
GGA = 91

NPAR=16



POSCAR

Si, fcc , 9 layer , (001)
5.456000000000000
1.4142135623730950 0.0000000000000000 0.0000000000000000
0.0000000000000000 0.7071067811865475 0.0000000000000000
0.0000000000000000 0.0000000000000000 5.0000000000000000
18 4
Selective dynamics
Direct
0.1000000000000000 0.0000000000000000 0.3999999999999986 T T T
0.4000000000000000 0.0000000000000000 0.3999999999999986 T T T
0.5000000000000000 0.5000000000000000 0.3500000000000014 T T T
0.0000000000000000 0.5000000000000000 0.3500000000000014 T T T
0.7500000000000000 0.5000000000000000 0.2999999999999972 T T T
0.2500000000000000 0.5000000000000000 0.2999999999999972 T T T
0.7500000000000000 0.0000000000000000 0.2500000000000000 T T T
0.2500000000000000 0.0000000000000000 0.2500000000000000 T T T
0.5000000000000000 0.0000000000000000 0.2000000000000028 T T T
0.0000000000000000 0.0000000000000000 0.2000000000000028 T T T
0.5000000000000000 0.5000000000000000 0.1499999999999986 F F F
0.0000000000000000 0.5000000000000000 0.1499999999999986 F F F
0.7500000000000000 0.5000000000000000 0.1000000000000014 F F F
0.2500000000000000 0.5000000000000000 0.1000000000000014 F F F
0.7500000000000000 0.0000000000000000 0.0499999999999972 F F F
0.2500000000000000 0.0000000000000000 0.0499999999999972 F F F
0.5000000000000000 0.0000000000000000 0.0000000000000000 F F F
0.0000000000000000 0.0000000000000000 0.0000000000000000 F F F
0.8525621922027579 0.0000000000000000 0.9578160190072483 F F F
0.1474753961681461 0.0000000000000000 0.9578283262895978 F F F
0.3524151067369008 0.0000000000000000 0.9577873239839876 F F F
0.6474544304642952 0.0000000000000000 0.9578145366380445 F F F

[admin]

1) please read the literature concerning the discussion of the electronic structure
of the 2x1-reconstructed Si(100) surface.
2) to exhibit a bulk-like electronic structure of the central Si atoms, your slab certainly is not thick enough