[Pw_forum] phonon dispersion

[Mehrnaz Anvari]

Hi
I've tried to plot phonon dispersion of graphene in gamma ,M,K,gamma 
direction. Although I used asr=crystal in my calculations, the acoustic 
phonons at first gamma point are not exactly zero. what is the reason of 
this happening? does it relate to choosing c/a in difinition of graphene?
Mehrnaz
 
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