[Pw_forum] phonon mode and atom displacements

[yumin qian]

>       Atomic displacements:
>      There are  16 irreducible representations
>
>      Representation     1      2 modes - To be done
>      Phonon polarizations are as follows:
>
                           mode #   1                           mode #   2
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (  -0.70711   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (  -0.70711   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.70711   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.70711   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000   )
           (   0.00000   0.00000   )            (   0.00000   0.00000


    I wander how the atoms ,in the unit cell are displaced, for a real
calculation

>    what's the relation between polariztion vector and atoms displacements
>
    and the relation between phonon mode , how to use the symmetry group to
    get the atoms displacements pattern ,  if the crystal have inversion
symmetry ,
   so is it correct to say a particular phonon mode have or not have
inversion symmetry.

>
> --
> Sincerely Y. M. Qian
> Lab.of Condensed Matter Theory and Materials Computation
> Institute of Physics
> Chinese Academy of Sciences
> Tel:  + 8610 8264 9147
> E-Mail:yuminqian at gmail.com <E-Mail%3Ayuminqian at gmail.com>
> P.O.Box 603   Beijing 100190
> China
>
>
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