On Monday 22 May 2006 18:15, Virginie Trinit? wrote: > I have a question about the subroutine random_matrix in PH > [...] I didn't understand why if nb is never the transform of na > by some symmetry then the dynamical matrix is zero?
the comment in the header of that subroutine reads: ! Create a random hermitian matrix with non zero elements ! similar to the dynamical matrix of the system but this is somewhat misleading. From what I remember the random matrix is used to find the irreducible representations of the small group of q (the phonon wavevector). If no symmetry sends atom na into atom nb, displacements of atoms na and nb will belong to different irreps. Disclaimer: I didn't write, and never really understood, how symmetry works in the phonon code, so the above might be all wrong! Paolo -- Paolo Giannozzi e-mail: giannozz at nest.sns.it Scuola Normale Superiore Phone: +39/050-509876, Fax:-563513 Piazza dei Cavalieri 7 I-56126 Pisa, Italy
