[Pw_forum] weird phonon frequencies for 3X 3X 1 KPOINTS

[Gabriele Sclauzero]

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/Türkiye
> Tel: 0090 312 290 3527 ; Fax: 0090 312 266 4365
> UNAM-web  : www.nano.org.tr <http://www.nano.org.tr>
>
>
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>    


-- 

Gabriele Sclauzero, EPFL SB ITP CSEA
PH H2 462, Station 3, CH-1015 Lausanne

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