Does the scf calculation find the expected symmetry ? then I'm surprised that the dynamical matrix does not show it. Does the structure look as it should when visualized with xcrysden ? Are you providing the atomic coordinates with enough digits ?
stefano - Stefano de Gironcoli - SISSA and DEMOCRITOS On 05/12/2011 10:38 PM, Paolo Giannozzi wrote: > On May 12, 2011, at 17:43 , mayank gupta wrote: > >> The phonon frequency for cubic crystal should have degenerate >> along [1 0 0] for TA modes, But i got different frequency. I have >> calculate the same with larger value of ecut_rho as well as with >> higher FFT mesh and still they are non degenerate. > symmetry doesn't change with the cutoff. You may want to try > a tighter convergence criterion (tr2_ph) > > P. > --- > Paolo Giannozzi, Dept of Chemistry&Physics&Environment, > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy > Phone +39-0432-558216, fax +39-0432-558222 > > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum
