SCF convergence problem with one anion in a box

[dyu]

I have trouble for SCF convergence for an anion in a vacuum box.
Does anyone have suggestions? Below is my input file.
Thanks you.

# Definition of the unit cell
#The length of the primitive vectors
# 1 Bohr=0.5291772108 Angstroms
# acell 10.497600 10.497600 25.000000 Angstroms
acell 19.837589 19.837589 47.243153
rprim
1.000000 0.000000 0.000000
0.000000 1.000000 0.000000
0.000000 0.000000 1.000000

#Definition of the atom types
# 10 kind of atoms
# ['H', 'C', 'O']
ntypat 3
znucl 1 6 8

#Definition of tha atoms
natom 10
typat 1 1 1 1 1 2 2 2 3 3
xred
0.54953 0.488194 0.263709
0.597746 0.44301 0.198492
0.40342 0.654867 0.224919
0.436457 0.598672 0.159489
0.558207 0.677447 0.197446
0.477334 0.610456 0.199734
0.516663 0.480623 0.22194
0.409358 0.378494 0.219028
0.345217 0.374438 0.176113
0.396924 0.306535 0.25944

#Basis definitions
ecut 20
ecutsm 0.5
pawecutdg 30.

#geometry optimziation
ionmov 2 # Use the modified Broyden algorithm
ntime 100 # Maximum number of Broyden "timesteps"
tolmxf 5.0d-5 # Stopping criterion for the geometry optimization : when

# the residual forces are less than tolmxf, the Broyden
# # algorithm can stop

#SCF cycle parameters
tolvrs 1.0d-10
nstep 200

#K-points and sym
kptopt 0 # Enter the k points manually
nkpt 1 # one k point

#dielectric
diemac 1.5

charge -1

pawovlp 15.0

usepotzero 2
#parallization parameters
autoparal 1

#I/O parameters
prtwf 1 prtden 0 prteig 0
getwfk -1

[gmatteo]

I would suggest to look at the eigenvalues to understand what's happening.
If there are degeneracies, you may try to use tsmear and a "metallic occupation scheme.
See: http://www.abinit.org/doc/helpfiles/for ... tml#occopt