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Dear Shuai,<br>
I've attached the input files to do it in "the right way". You can
see three ways to compute the energy of the isolated Oxygen atom,
but only the one that gives the lowest energy is correct! Try to see
for yourself what are the differences between the three cases, and
please ask if you have any doubt.<br>
<br>
Also for the O2 molecules theer are some tricks to use, again ask if
you have doubts.<br>
<br>
Finally, note that the O-O oxygen in the molecule is very small,
smaller that the pseudisation radius normally used in
pseudopotential. This means that if you want to get really accurate
results you will have to find or generate an especially hard
pseudopotential.<br>
<br>
kind regards<br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 17/01/15 07:53, Shuai wrote:<br>
</div>
<blockquote cite="mid:54BA06D7.60007@edu.life.kyutech.ac.jp"
type="cite">
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charset=windows-1252">
Dear all,<br>
<br>
I want to calculate the energy of the O2 in its triplet ground
state. I have searched on the sites (<a moz-do-not-send="true"
class="moz-txt-link-freetext"
href="http://qe-forge.org/pipermail/pw_forum/2012-July/099147.html">http://qe-forge.org/pipermail/pw_forum/2012-July/099147.html</a>)
and do some tentative calculations.<br>
<br>
Firstly, I calculated the two O atoms in a enough large box. the
input file is:<br>
<br>
<small> &control<br>
calculation = 'relax'<br>
prefix = 'O2'<br>
pseudo_dir = '/'<br>
outdir = '/'<br>
/<br>
&system<br>
ibrav = 1, celldm(1) = 30.0<br>
nat = 2, ntyp = 1,<br>
ecutwfc = 35, ecutrho = 280<br>
occupations = 'smearing', degauss = 0.01<br>
nspin = 2, starting_magnetization(1) = 0.3<br>
/<br>
&electrons<br>
mixing_mode = 'plain'<br>
mixing_beta = 0.3<br>
conv_thr = 1.0d-8<br>
electron_maxstep = 200<br>
/<br>
&ions<br>
ion_dynamics = 'bfgs'<br>
/<br>
ATOMIC_SPECIES<br>
O 15.999 O.pbe-n-kjpaw_psl.1.0.0.UPF<br>
ATOMIC_POSITIONS {angstrom}<br>
O 5.000576334 5.029093041 5.029093041<br>
O 5.009423666 5.870906959 5.870906959<br>
K_POINTS {gamma}</small><br>
<br>
Secondly, I calculated the single O atom.<br>
<br>
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?<br>
<br>
Thanks in advance.<br>
<br>
Sincerely,<br>
<br>
S. Zhao<br>
--<br>
PhD candidate<br>
Graduate School of Life Science and Systems Engineering<br>
Kyushu Institute of Technology, Japan <br>
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<pre class="moz-signature" cols="72">--
Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
+33 (0)1 44 275 084 / skype: paulatz
<a class="moz-txt-link-freetext" href="http://www-int.impmc.upmc.fr/~paulatto/">http://www-int.impmc.upmc.fr/~paulatto/</a>
23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05 </pre>
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