bader tells different atomic charges of O2

[hakuna]

Dear all
just a simple system of O2
***
system= O2
1.00000000000000
14.0000000000000000 0.0000000000000000 0.0000000000000000
0.0000000000000000 16.0000000000000000 0.0000000000000000
0.0000000000000000 0.0000000000000000 18.0000000000000000
O
2
Selective dynamics
Direct
0.5000000000000000 0.5000000000000000 0.5342472313401530 T T T
0.5000000000000000 0.5000000000000000 0.4657527686598470 T T T
***
optimized and then calculate the bader charges(PAW-PBE)
the ACF.dat:
# X Y Z CHARGE MIN DIST ATOMIC VOL
--------------------------------------------------------------------------------
1 7.000000 8.000000 9.616446 5.863994 0.526446 2075.275300
2 7.000000 8.000000 8.383554 6.136010 0.616446 1956.724700
--------------------------------------------------------------------------------
VACUUM CHARGE: 0.0000
VACUUM VOLUME: 0.0000
NUMBER OF ELECTRONS: 12.0000

why the two O atoms have different charges?

[graeme]

Try reducing the grid spacing using the NGXF, NGYF, and NGZF. Also try using the -b weight method.