[Pw_forum] Negative Phonon Frequencies - Numerical instability or unstable structure

[Pietro Delugas]

Then one of the 3 acustic branches ( probably the one you gave problems 
with ) should be flat.

I don't know how this phononpy works,  maybe there is a way to deal 
directly with 2D systems, otherwise just find a way to set to 0 all the 
interatomic force constants that  correspond to interactions between 
atoms staying in different periodic images of the slab.


pietro



On 05/12/2016 09:33, Mohammed Ghadiyali wrote:
>
> Hi,
>
>
> The structure is two dimensional similar to bi-layer graphene.
>
>
> Regards,
>
>
> Ghadiyali Mohammed Kader
>
>
> Research Scholar
>
>
> University of Mumbai.
>
>
>
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