[Pw_forum] phonon

stefano de gironcoli degironc at sissa.it
Tue Apr 7 21:45:50 CEST 2015

if the calculation is properly converged an imaginary frequency (printed 
as negative in the output) signals a structural instability for atoms 
moving according to the vibrational pattern.

To find the new structure look for a supercell for which the given 
q-vector would be folded in Gamma, slightly displace the atoms according 
to the unstable vibrational pattern and relax.


On 06/04/2015 17:31, Masoud Avi wrote:
> Hi
> I've calculated the phonon distribution, But at a point other than the 
> gama point is negative frequency !!
> What is the reason? and What to do?
> thanks
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> Pw_forum at pwscf.org
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