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I am unable to reproduce the O2 binding energy reported in JCP 122, 234102 (2005), I get 160.6kcal/mol, not 143.3kcal/mol. I am attaching my input decks. it would be nice if I could get a copy of a deck that does reproduce the O2.
O atom input
output=$KEEP/$0.out
date >$output
cat /pgm/lawson/vasp/potpaw_PBE/O_h/POTCAR >POTCAR
#
cat <<! >KPOINTS
1 Kpoints
0
Gamma
1 1 1
0 0 0
!
cat <<! >INCAR
System = O

ISTART=0
ISPIN=2
NUPDWN=2
ISIF=2
NSW= 0
POTIM= 0.01
ISMEAR=0
SIGMA=0.02
ALGO=Normal
PREC=High

IBRION=2
!
cat >POSCAR <<!
O atom
1.00
10. 0.00000000 0.00000000
0.00000000 10.0 0.00000000
0.0 0.0 10.00
1
cart
5.0 5.0 5.0
!
/pgm/bauschli/vasp/vasp.4.6/vasp
cat OUTCAR >>$output

O2 input
KEEP=`pwd` # home directory for permanent files
output=$KEEP/$0.out
date >>$output
cat /pgm/lawson/vasp/potpaw_PBE/O_h/POTCAR >POTCAR
#
cat <<! >KPOINTS
1 Kpoints
0
Gamma
1 1 1
0 0 0
!
cat <<! >INCAR
System = O2
ISTART=0
ISIF=2
NSW=0
POTIM= 0.01
ISPIN=2
ISMEAR =0
SIGMA=0.02
ALGO=Normal
NUPDOWN=2
IBRION=2
RWIGS= 1.4 1.4
LORBIT=.True.
PREC=High

!
cat >POSCAR <<!
O2
1.00
10. 0.00000000 0.00000000
0.00000000 10.0 0.00000000
0.0 0.0 10.00
2
cart
5.00000 5.00000 4.99212
5.00000 5.00000 6.20788
!
/pgm/bauschli/vasp/vasp.4.6/vasp
cat OUTCAR >>$output

please reduce the symmetry of the box for the O-atom calculation from cubic (eg to slightly tetragonal or orthorhombic). this will reduce the energy of the free atom significantly. (please have a look at the handsonI.pdf file of the vasp-workshop tutorials
(http://cms.mpi.univie.ac.at/vasp-workshop)

thanks, that fixes it. An interesting aside is that the effect of lowering the symmetry at the Hartree-Fock level using a Gaussian basis sets is 1.2 kcal/mol per atom.