[Pw_forum] Is maxirr=N working in phonon calculations?

Serge Nakhmanson nakhmanson at anl.gov
Thu Nov 6 20:03:12 CET 2008

Dear Stefano,

Thank you for the clarification.


Stefano Baroni wrote:

>> I only know a general answer to how it is done -- by induction
>> from an (Abelian) group of crystal translations -- but am
>> rusty on particular numerical algorithms. However, I got an
>> excellent new book by El-Batanouny and Wooten (ISBN 9780521828451),
>> all the details should be in there.
> I do not know about the book, but I am afraid that what is implemented 
> in the code is not anything worth reporting in a book. The idea is as 
> follows. The code already contains all the weaponery for simmetrizing 
> all kind of stuff with respect to the small group of the point in the 
> Brillouin zone we are working at. In particular, you fill the dynamical 
> matrix with random numbers and then symmetrize it. The resulting matrix 
> will commute with all the operations of the small group, and its 
> eigenvectors will therefore realize a number of irreducible 
> representation of the group. As simple as that. Do not ask me about the 
> details of the implementation, though. The documentation (as poor as it 
> may be) is the code itself ...

  Serge M. Nakhmanson               phone: (630) 252-5205
  Assistant Scientist                 fax: (630) 252-4798
  MSD-212, Rm. C-224
  Argonne National Laboratory
  9700 S. Cass Ave.
  Argonne, IL 60439

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