[Pw_forum] phonon symmetry at any point

[Dr. Claire Loison]

Dear all,

My question has probably been answered
already somewhere, but I could not 
find any hint in the mailing-list.

=> Here are my questions:
Is there a tool (in espresso or somewhere else)
that analyzes the symmetry of the
eigenvectors of the dynamical matrix ?
Can ph.x give this information in the output ? 
Does ph.x use symmetry arguments
to simplify the diagonalizing of the dynamical matrix ?

=> Here is the background, in case my question are not precise enough:
When I calculate the phonon dispersion of a solid,
I get the phonon frequencies and eigenvectors at any q-point.
As many have done before me, I want to link the frequencies at different 
qpoints according to their symmetry properties.
For the gamma point, i can relatively easily attribute the symmetry to the 
different modes by looking at the eigenvectors of the dynamical matrix.
But for other q-points, it gets much more 
complicated. I suppose i should find the sub-group of the new enlarged 
unit cell corresponding to the new q-point
and find there which are the new symmetry of the modes in this subgroup.
And then finally see how they correlate to the symmetries found at gamma 
point.  I can do this procedure by hand a few times for high-symmetry 
qpoints, but for any q-point, i would just like to have a nice code 
helping me to avoid  errors and saving time...
Do you know of such a tool ?

Thank you in advance,

Claire


___________________________________________
Dr. Claire LOISON
http://www.cpfs.mpg.de/~loison/
MPI fuer Chemische Physik fester Stoffe
Noethnizerstrasse 40
D- 01187 Dresden
GERMANY

e-mail : loison at cpfs.mpg.de
tel : +49-351-4646-4225
fax : +49-351-4646-10
___________________________________________