[Pw_forum] Displacements corresponding to -ve Phonon modes

[Stefano Baroni]

On Oct 4, 2010, at 3:07 PM, Bipul Rakshit wrote:

> Dear PWSCF users,
> 
> I am doing Phonon  of KO2 compound.  I find some -ve phonon modes at gamma point.  (After applying  ASR also)
> Following is the  dynamical matrix  formed by the phonon programme during the run.
> I just want to study the displacement corresponding to -ve modes. So Is it enough to plot the eigen vectors given below corresponding to each mode.
> Strange things what I feel in these eigen vectors are the 'K' is also moving almost with the same magnitude as 'O'

Not so strange for zone-center acoustic modes (their frequency is zero exactly because they correspond to a rigid translation)

> and there is no imaginary part of eigen vectors though the frequencies are -ve.

why should there be any?

what do you mean by "-ve"?

SB


---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center - Trieste
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