Yes, I perfectly agree with Eyvaz! Moreover the experimental bandgap is underestimated within LDA or GGA, and for 4H-SiC you would get about 2.2-2.3 eV with LDA.
How do you measure the bandgap? Beware that in the fundamental cell the bandgap is not a direct one, but it might become such when you use a supercell (because of the refolding of the Brillouin zones). HTH GS Il giorno 03/apr/2011, alle ore 10.59, Eyvaz Isaev ha scritto: > Hi, > > >The bandgap of 8-atoms is around 10-12 eV, > >but that of 72-atom is around 5-7 eV. > > This is unbelievable, as SiC is an indirect band gap semiconductor and > the bandgap is around (2.5 - 3)eV depending on crystal modification > (3C-SiC, 2H-SiC; 4H-SiC; 6H-SiC, etc.). > See http://www.matprop.ru/SiC_bandstr > > So, check carefully your input/output files. > > Bests, > Eyvaz. > > ------------------------------------------------------------------- > Prof. Eyvaz Isaev, > Department of Physics, Chemistry, and Biology (IFM), Linkoping University, > Sweden > Theoretical Physics Department, Moscow State Institute of Steel & Alloys, > Russia, > isaev at ifm.liu.se, eyvaz_isaev at yahoo.com > > > From: pari shok <parishok at gmail.com> > To: pw_forum at pwscf.org > Sent: Sun, April 3, 2011 1:34:51 AM > Subject: [Pw_forum] shift of energy > > Dear Paolo, > DOS of 72-atom SiC shows a shift of energy with respect to 8-atom SiC.The > bandgap of 8-atoms is around 10-12 eV, but that of 72-atom is around 5-7 eV. > Would you please help me to understand this shift. > > Thanks again. > P Shok > UMD > On Apr 1, 2011, at 21:36 , pari shok wrote: > > > The DOS of 72-atom SiC (supercell) shows a shift of energy. > > a shift with respect to what? > --- > Paolo Giannozzi, Dept of Chemistry&Physics&Environment, > > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy > Phone +39-0432-558216, fax +39-0432-558222 > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum ? Gabriele Sclauzero, EPFL SB ITP CSEA PH H2 462, Station 3, CH-1015 Lausanne -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110404/3b12b706/attachment.htm