[Pw_forum] binding energy of molecular oxygen

[Lorenzo Paulatto]

How did you compute EO? You need to use spin polarization and to break 
symmetry in order to get the lowest possible energy (i.e. Hund's rule).

kind regards

On 04/28/2014 10:06 AM, Junxiang Chen wrote:
>
> Dear all,
>
> The same problem as 
> http://qe-forge.org/pipermail/pw_forum/2009-November/089525.html , the 
> binding energy of detached O2 is 6.57eV, which is far from experiment 
> value ( 5.12eV ), or 5.7eV in this page.
>
> Input file ( O2 ):
>
> &SYSTEM
>
> ibrav = 12,
>
> celldm(1) = 16.0348541363689,
>
> celldm(2) = 1.52752767,
>
>      celldm(3) = 2.665651575,
>
> celldm(4) = -0.3273333438252,
>
> nat = 2,
>
> ntyp = 1,
>
> ecutwfc = 45,
>
> ecutrho = 400,
>
> occupations = 'smearing' ,
>
> degauss = 0.01,
>
> smearing = 'methfessel-paxton' ,
>
> nspin = 2,
>
> starting_magnetization(1) = 1,
>
> /
>
> &ELECTRONS
>
> electron_maxstep = 200,
>
>                  conv_thr = 1.D-6,
>
> mixing_beta = 0.4,
>
> mixing_mode = 'local-TF' ,
>
> /
>
> &IONS
>
> ion_dynamics = 'bfgs' ,
>
> /
>
> ATOMIC_SPECIES
>
>    O     15.9994 O.pbe-rrkjus.UPF
>
> ATOMIC_POSITIONS crystal
>
> O        0.217969593 0.389882242   0.401960243
>
> O        0.217971037 0.389881524   0.456565745
>
> K_POINTS automatic
>
>   5 5 2   0 0 0
>
> The binding energy is calculated by BE=EO2-2*EO* and BE=6.57eV
>
> Could anyone tells me what's wrong?
>
> -------------------------------------------------------
>
> Junxiang Chen
>
> Ph.D. candidate
>
> Department of chemistry and molecular
>
> Wuhan University
>
> Wuhan, China
>
> Email: cjxxjc729 at gmail.com <mailto:cjxxjc729 at gmail.com>
>
> -------------------------------------------------------
>
> Junxiang Chen
>
> Ph.D. candidate
>
> Department of chemistry and molecular
>
> Wuhan University
>
> Wuhan, China
>
> Email: cjxxjc729 at gmail.com
>
> QQ: 95508097
>
>
>
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-- 
Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
+33 (0)1 44 275 084 / skype: paulatz
http://www-int.impmc.upmc.fr/~paulatto/
23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05

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