[Pw_forum] matdyn.x

[S. K. S.]

Dear Stefano,

Thanks a lot for your quick reply.
Yes, both set of the frequencies are
obtained after imposing ASR. All of
frequencies are not negative.  Two of
the modes among total 5 modes
(triply generate) are negative, which are
not very unusual in a BaTiO3-type cubic
perovskite.

regards,
Saha S. K.


On 5/11/11, Stefano de Gironcoli <degironc at sissa.it> wrote:
> are you imposing acoustic sum rule  ? this change slightly the frequencies .
> isn't strange that your frequencies are all negative (imaginary) ?
> is your system stable ?
> stefano
>