Why work function varies with SIGMA ?

[des]

Hello everyone,
I am doing calcs to get the correct work function of a system. It seems in my result the work function varies with different values of SIGMA keeping all other parameters constant. I used SIGMA fro 0.001 to 0.2. In all the range the change in the free enrygy and the T*S term is much less than 1meV. Large vacuum thickness is used.
My INCAR is
SYSTEM = Surface
ISYM=2
LSCALAPACK =.FALSE.
NELMIN= 5
PREC= Accurate
ALGO=Very Fast
ENCUT=325
IDIPOL=3
LDIPOL=.TRUE.
LVTOT=.TRUE.
ISMEAR=0
SIGMA = 0.15
NSW= 500
ISIF = 2
IBRION = 2
POTIM = .1
LREAL= Auto

Could you please tell me where my mistake is ? Or any suggestion .
Thank you

<span class='smallblacktext'>[ Edited ]</span>

[admin]

to get accurate results of the Fermi level (and band structure data in general), please, after having reached ionic convergence:
continue from the converged CHGCAR (ICHARG=11)
1) choose ISMEAR = -5
(you may have to switch to a different k-mesh)
2) increase the number of k-points
3) increase NEDOS, the default value of 301 may be too small if your energy spectrum covers a wide range)

[des]

Hello Adm,
Thank you. Well done!