[Pw_forum] zone center phonons of Si lattice

[Ezad Shojaee]

Hi
It seems that if we look to Si lattice as an SC with 8 atoms per cell, the symmetries connected to the fractional translations will not be accepted, so if we use this scheme to obtain the zone-center phonons of Si, we will get frequencies rather different from the main one(FCC scheme), with different symmetries and degenerecies.
How is it possible to obtain the right ones (zone-center phonons) of Si, with the right symmetries and degenerecies, by the SC scheme?
Thanx 
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