Hi,
I don't understand what kind of technique you expect. The handling of
tensor using matrix representations of space group can be found in the
books for group theory for solids. I think the best is to read one of
those books.
By the way, phonopy does not directly apply symmetry constrains numerically.
http://phonopy.sourceforge.net/theory.html#thepalinskilikawazoemethod
Togo
On Wed, Mar 27, 2013 at 4:02 AM, Iyad ALQASIR <iyad.ne@...> wrote:
> Dear Phonopy users,
>
> Phonopy calcualted the nonequivalent set of force constants and distribute
> them to those are equivalent. It applies also symmetry operations on the
> force constants to conserve the clousre relations ( constraints). But all of
> this is done numerically.
>
> My question, how for a system of given number of atoms, I can extract
> analytically using phonopy the list of the nonequivalent force constants
> and the equations connect these force constants based on the symmetry
> operations. As an example for a system of Nb using 54 atoms which means
> there are 54 x 54 matrix element where each element is 3x3 matrix, that is,
> there are 26244 force constants, only 16 force constants are nonequivalent.
> I did that by hand which is time consuming. If I want to know the
> relations between these force constants, please advice how.
>
> Thank you
> ___________________________
> IYAD I. ALQASIR, PhD
> Postdoc Research Associate
>
> XRay and Neutron Scattering and Spectroscopy Group
> Materials Science and Technology Division
> Oak Ridge National Lab
> Oak Ridge, TN
>
> 
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Atsushi Togo
http://atztogo.github.com/
atz.togo@...
