[Pw_forum] binding energy of molecular oxygen

Lorenzo Paulatto lorenzo.paulatto at impmc.upmc.fr
Mon Apr 28 10:24:07 CEST 2014


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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