[Pw_forum] zone center phonons of Si lattice

[Paolo Giannozzi]

On Nov 28, 2007, at 14:14 , Ezad Shojaee wrote:

> 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.

not at all. If you do things properly, you will get the modes you
should get, with or without symmetry imposed, apart from
minor losses of symmetry due to incomplete convergence

Paolo
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Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222