[Pw_forum] Energy of O2 in its triplet ground state

[Shuai]

Dear all,

I want to calculate the energy of the O2 in its triplet ground state. I 
have searched on the sites 
(http://qe-forge.org/pipermail/pw_forum/2012-July/099147.html) and do 
some tentative calculations.

Firstly, I calculated the two O atoms in a enough large box. the input 
file is:

  &control
    calculation    = 'relax'
    prefix    = 'O2'
    pseudo_dir    = '/'
    outdir    = '/'
  /
  &system
    ibrav = 1, celldm(1) = 30.0
    nat = 2, ntyp = 1,
    ecutwfc = 35, ecutrho = 280
    occupations = 'smearing', degauss = 0.01
    nspin = 2, starting_magnetization(1) = 0.3
  /
  &electrons
    mixing_mode    = 'plain'
    mixing_beta    = 0.3
    conv_thr    = 1.0d-8
    electron_maxstep = 200
  /
  &ions
    ion_dynamics    = 'bfgs'
  /
ATOMIC_SPECIES
O    15.999    O.pbe-n-kjpaw_psl.1.0.0.UPF
ATOMIC_POSITIONS {angstrom}
O    5.000576334    5.029093041    5.029093041
O    5.009423666    5.870906959    5.870906959
K_POINTS {gamma}

Secondly, I calculated the single O atom.

Finally, I calculated the binding energy of O2 by "2 x single O atom 
energy - O2 eneygy". But I am not sure it is correct or not. My question 
is if the "binding energy" is close to the experimental value ~ 5.7 eV, 
does it mean that the calculated energy of O2 is accurate?

Thanks in advance.

Sincerely,

S. Zhao
--
PhD candidate
Graduate School of Life Science and Systems Engineering
Kyushu Institute of Technology, Japan
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