[Pw_forum] phonon mode and displace pattern

[yumin qian]

     There are several  things I don't know about the phonon dispersion
analysis
    1  How to discern  longitudinal   and  transverse mode ?
    2  In the process of dynamic matrix construction , for a  particular
mode how to displace atoms ,
         I don't think I  know the real meaning of "displacements along
irreps of decomposed 3N-dimensional representation ",
    3  How to tell which mode does a dispersion curve belongs to ?
    4  If I want to see a particular mode , how should I choose the
parameter of : nrapp
    5  if I want to see  a particular atom or a subset of atoms displace,
such as in p4/mmm  SrCrO3 crystal ,fix Sr,Cr and let O displace ,how should
I choose the parameter:  nat_todo, and so only part of the modes of this
crystal are caculated , ,how to tell which mode are they belong to.


ATOMIC_POSITIONS
Sr       0.500000000   0.000000000   0.412027344
Sr       0.000000000   0.500000000   0.412027344
Cr1      0.000000000   0.000000000   0.058596874
Cr2      0.500000000   0.500000000   0.058594869
O        0.000000000   0.000000000   0.412132248
O        0.500000000   0.500000000   0.412139067
O        0.250003893   0.250003893   0.058620564
O        0.250003893   0.749996107   0.058620564
O        0.749996107   0.250003893   0.058620564
O        0.749996107   0.749996107   0.058620564



Many thanks

-- 
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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