[Pw_forum] Convergence of Phonon with K points

[Prasenjit Ghosh]

For which phonons are you getting the imaginary frequencies?

If it is for the acoustic modes at gamma point, then it tells that
your structure is not stable.....however if it is for other k-points,
it is an indication that your cell parameters are not well optimized.

Prasenjit

On 10 August 2011 13:14, mayank gupta <mayankaditya at gmail.com> wrote:
> Dear Sir
>
> It's magnetic oxide SrFeO2. Kohn anomaloy occurs in metallic system.
> Should I further increase k points or do something else.
>
> Thanks
>
>
>> it may depend on a Kohn anomaly (which are particularly sensitive to k-point sampling)
>> SB
>>
>> On Aug 9, 2011, at 9:24 AM, mayank gupta wrote:
>>
>>> Dear all
>>>
>>>
>>> I am doing phonon calculation of a magnetic system,  have not included
>>> any magnetic interaction on it. I am calculating phonon at  2x2x2 mesh
>>> (6 q points). I got the phonon frequency +ve at 5 q point  while at
>>> one q point it is negative. I have check this with 24 x24x24 k point
>>> and with very high ecut and observed  this particular phonon mode
>>> doesn't converge with k point while rest is converged. is it because
>>> of not taking in to account the magnetic part or something else.
>>>
>>>
>>>
>
> --
> Mayank
>
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PRASENJIT GHOSH,
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