The ABINIT Users Mailing List ( CLOSED )

[Aloysius Soon <aloysius@physics.usyd.edu.au>]

Dear all,
I've been playing around for quite a while with various 
examples found in the Test_v* and Tut, but I can't seem to 
get the right answer for a simple (although not that simple) 
like O2 molecule in a box. Upon subtraction, the binding 
energy that I've got out of a typical GGA calculation is 4 
to 5 eV per O atom, which is way-off the usual that 
literature or other codes I've used (~3.1 to 3.3 eV). I've 
attached one of the many input files that I've used for the 
atom and molecule. Hope someone could help me out in this.

Many thanks.

== input file for oxygen atom ==
occopt 3           # Could not converge with default
tsmear 0.03 eV
#band  16
#iscf   17
#npulayit 3
nsym  1
nsppol 2           # Needed for spin-polarized run
kptopt 0
kpt    0.25 0.25 0.25

#Definition of the unit cell
acell   9.0   10.0   11.0 angstrom
#angdeg  90  90  90
rprim
              1.00000000000000    0.00000000000000 
0.00000000000000
              0.00000000000000    1.00000000000000 
0.00000000000000
              0.00000000000000    0.00000000000000 
1.00000000000000
chkprim 0

#Definition of the atom types
ntypat 1
znucl  8

#Definition of the atoms
natom 1
typat 1
xred
            0.00000000000000    0.00000000000000 
0.00000000000000

#Exchange-correlation functional
ixc 11             # GGA-PBE

#Definition of the planewave basis set
ecut         70.0 Ry


#Definition of the SCF procedure
nstep 99
toldfe 1.0d-12
#tolvrs 1.0d-8
diemac 1.5
diemix 0.5
===EOF===

== input file for oxygen molecule ==
occ 1.0  1.0  1.0  1.0  1.0  1.0  1.0  0.0
    1.0  1.0  1.0  1.0  1.0  0.0  0.0  0.0
occopt 2
nsppol 2
nband  8 8
nsym  1
kptopt 0
kpt    0.25 0.25 0.25

#Definition of the unit cell
acell     9.0   10.0   11.0 angstrom

#angdeg  90  90  90
rprim
              1.00000000000000    0.00000000000000 
0.00000000000000
              0.00000000000000    1.00000000000000 
0.00000000000000
              0.00000000000000    0.00000000000000 
1.00000000000000
chkprim 0

#Optimization of the lattice parameters
optcell 0
ionmov  3
ntime   99
dilatmx 1.1
ecutsm  0.5
prtgeo  2

#Definition of the atom types
ntypat 1
znucl  8

#Definition of the atoms
natom 2
typat 1 1
xangst
              0.00000000000000     0.00000000000000 
0.60856624824230
              0.00000000000000     0.00000000000000 
-0.60856624824230

#Exchange-correlation functional
ixc 11             # GGA-PBE

#Definition of the planewave basis set
ecut         70.0 Ry

#Definition of the SCF procedure
nstep 99
toldfe 1.0d-8
diemac   1.5
diemix   0.5
===EOF===



Best regards,
Aloysius

--
Aloysius Soon
Condensed Matter Theory Group
School of Physics A28, Room 361
The University of Sydney, NSW 2006 Australia
Phone: +61 2 903 65389
Fax: +61 2 935 17726
Email: aloysius@physics.usyd.edu.au
Web: http://www.physics.usyd.edu.au/~aloysius/
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"Gather ye rosebuds while ye may,
Old time is still a-flying,
And this same flower that smiles today,
To-morrow will be dying."
                        ROBERT HERRICK
                        1591-1674
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