Dear Gabriele, Thank you very much for your suggestion. After including some smearing, -5000 frequencies disappeared. But this still cannot explain the 3X 3X 1 situation. For this reason, I plotted the positions of scf KPOINTS (see the attachments) and realized that the corner of the Brillouin zone, which is also known as K-special-point, is NOT included for KPOINTS other than 3X 3X 1. For graphene, K-special-point also corresponds to the Dirac-Point where zero-band-gap occurs. As a result, problem should be related with K-special-point.
BUT. Still I cannot understand why inclusion of a point in BZ corresponds to such a HUGE difference in phonon frequencies. Maybe someone in this list gives a better explanation for that.... All of the files are available at http://db.tt/xK2Jtu1 Ragards. On Thu, Sep 30, 2010 at 4:47 PM, Gabriele Sclauzero <sclauzer at sissa.it>wrote: > Dear Mehmet, > > graphene has zero gap, hence you probably need to include smearing of > the occupations in the scf calculations. > > > HTH > > GS > > > On 09/29/2010 04:54 PM, Mehmet Topsakal wrote: > > Dear all, > > For graphene structure, I noticed that I get completely wrong phonon > frequencies when I use KPOINTS such as 9 9 1, 12 12 1, 15 15 1 > > For example: > > K_POINTS {automatic} > 11 11 1 0 0 0 > > gives realistic frequencies as in 11.phonon.out file > > BUT > > K_POINTS {automatic} > 12 12 1 0 0 0 > > gives "omega( 1) = -149.592762 [THz] = -4989.910586 [cm-1]" as > in 12.phonon.out > > > What should be the reason ???? > > Thanks. > > -- > > Mehmet Topsakal (Ph.D. Student) > UNAM-Institute of Materials Science and Nanotechnology. > Bilkent University. 06800 Bilkent, Ankara/T?rkiye > Tel: 0090 312 290 3527 ; Fax: 0090 312 266 4365 > UNAM-web : www.nano.org.tr > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.orghttp://www.democritos.it/mailman/listinfo/pw_forum > > > > -- > > Gabriele Sclauzero, EPFL SB ITP CSEA > PH H2 462, Station 3, CH-1015 Lausanne > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > > -- Mehmet Topsakal (Ph.D. Student) UNAM-Institute of Materials Science and Nanotechnology. Bilkent University. 06800 Bilkent, Ankara/T?rkiye Tel: 0090 312 290 3527 ; Fax: 0090 312 266 4365 UNAM-web : www.nano.org.tr -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20100930/3d39d54a/attachment-0001.htm -------------- next part -------------- A non-text attachment was scrubbed... Name: BZ.png Type: image/png Size: 98121 bytes Desc: not available Url : http://www.democritos.it/pipermail/pw_forum/attachments/20100930/3d39d54a/attachment-0001.png -------------- next part -------------- A non-text attachment was scrubbed... Name: draw_bz.m Type: text/x-objcsrc Size: 9206 bytes Desc: not available Url : http://www.democritos.it/pipermail/pw_forum/attachments/20100930/3d39d54a/attachment-0001.bin
