[Pw_forum] Negative phonon frequency

[mohnish pandey]

Dear Mayank!
   There is no need to use this much high cutoff. First of all see proper
convergence with k-points grids. Then  "conv_thr" should be less than
10^-12. Before doing phonon calculation do vc-relax with high accuracy. And
if you get very small negative value then you can ignore it..


On Wed, May 11, 2011 at 3:18 PM, mayank gupta <mayankaditya at gmail.com>wrote:

> Hi Dear User's
>
>
> I am trying to calculate the phonon frequency of SrFeO compund, but I
> got negative frequancies at gamma also at other Q points, while I have
> chossen very high cutoff (ecut=100Ry and ecut_rho=1000), while
> experimentally the structure is stable at room temperature even up to
> very low temperature. what could be the possible reason for such
> negative frequecies.
>
> --
> Mayank
>
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-- 
Regards,
MOHNISH,
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Mohnish Pandey
Y6927262,5th Year dual degree student,
Department of Chemical Engineering,
IIT KANPUR, UP, INDIA
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