[Pw_forum] symmetry problem with Si lattice

[Ezad Shojaee]

Hi
in order to have the Gamma-point phonon frequencies, if we use the SC lattice schemma for Si, it seems that we have frequencies rather diffrerent from the FCC schemma. What do you expect of the irreps and the symmetries of the modes(and also their number) of SC schemma with 8-atom basis comparing to the FCC one(with 2 atoms per basis)? what should be the same in two shemmas?
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