converge problem of free atom energy calculation for Fe and Ni

[tracy]

Dear all,
I used paw_GGA potential to calculate the free atom energy of Fe and Ni. First I checked the configurations of these two atoms in the corresponding V_RHFIN files, they are Fe(3d74s1) and Ni(3d94s1). Then I used the procedure as http://cms.mpi.univie.ac.at/vasp/vasp/node231.html for the free atom energy calculation.
But for Fe I found the free-atom energy E0 varies with the smearing width, the results are as follows:
SIGMA=0.1 (not converge, even I set NELM=400 in INCAR, it stopped after 305 steps (the default maximum number of steps?)
SIGMA=0.01 -3.2510866
SIGMA=0.001 -3.0363088
SIGMA=0.0001 -3.2516864
SIGMA=0.00001 -3.2406304
Also for Ni it only converged when SIGMA=0.1 (-0.6095672)and 0.01(-0.36154525), for SIGMA=0.001, 0.0001 or 0.00001 the calculations stopped after 305 steps even I set NELM=400 in INCAR.
I have several questions to ask, hope you can help me! Thanks in advance!
1) Should I use the configurations of Fe and Ni in the periodic table of the elements which are Fe(3d64s2) and Ni(3d84s2) respectively for free atom energy calculation? If yes, how can I set FERWE and FERDO in INCAR for each atoms? Does anybody have some general examples of INCAR files where these tags have been used?
2)If the configurations in PAW_GGA (V_RHFIN) files are right, which are Fe(3d74s1) and Ni(3d94s1), how to understand the weird free atom energies variety with the SIGMA, which is the correct free atom energy for Fe atom?
3) If the configurations in PAW_GGA (V_RHFIN) files are right, which are Fe(3d74s1) and Ni(3d94s1), How to make the not-converged calculation for Ni and Fe converge? Thanks for any comments! Have a nice weekend!
The INCAR, KPOINTS and POSCAR files for all the above calculations are attached below:
INCAR:
ISYM=0
ISPIN=2
VOSKOWN=1
ISMEAR=0
SIGMA=0.1(or change to 0.01,0.001,0.0001,0.00001)
AMIX=0.2
BMIX=0.0001
NELM=400
ICHARG=1

KPOINTS:
K-Points
1
rec
0 0 0 1

POSCAR:
atom in a box
1.0
10 0 0
0 10.25 0
0 0 10.5
1
cart
0 0 0

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