Dear Junxiang Chen If you keep in mind that DFT-GGA is probably one of the less accurate ab-initio methods (also when you do your best), your result seems not to be "far from experiment value". I would rather write in a paper that such a result is "reasonably similar to the experimental value"...:-) HTH
Giuseppe Giuseppe Mattioli ISM-CNR Italy Quoting Junxiang Chen <cjxxjc729 at gmail.com>: > 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 -- ******************************************************** - Article premier - Les hommes naissent et demeurent libres et ?gaux en droits. Les distinctions sociales ne peuvent ?tre fond?es que sur l'utilit? commune - Article 2 - Le but de toute association politique est la conservation des droits naturels et imprescriptibles de l'homme. Ces droits sont la libert?, la propri?t?, la s?ret? et la r?sistance ? l'oppression. ******************************************************** Giuseppe Mattioli CNR - ISTITUTO DI STRUTTURA DELLA MATERIA v. Salaria Km 29,300 - C.P. 10 I 00015 - Monterotondo Stazione (RM) Tel + 39 06 90672836 - Fax +39 06 90672316 E-mail: <giuseppe.mattioli at ism.cnr.it>
