Can you give more information? Which system is it? Does the scalar relativistic phonon calculation have the correct symmetry?
A. On Tue, 2012-07-17 at 18:46 +0530, Koushik Pal wrote: > Dear sir, > I calculated the phonon frequencies of a system using both the > frozen phonon method as well as DFPT (ph.x) in fully relativistic > regime (spin-orbit interaction) using QE verson 4.3. According to > group theory the 12 optical modes of the system are 2A1g + 2Eg + 2A2u > +2Eu. I got accurate results for the frequncies in the frozen phonon > method (means, the frequencies obeyed the symmetry rule as predicted > by the group theory. Also I visualized the eigenmodes which also agree > well), but in the DFPT (linear response theory), the obtained > frequencies and eigenmodes do not obey the above symmetry principles > as predicted by group theory (though the frequencies are near the > frequencies as obtained in frozen-phonon method) . It seems that the > degeneracies in the frequencies are broken in DFPT. What is the reason > behind that? Please help. Please give references with mathematical > details (if available). > > Thanks in advance. > > ============= > Koushik > Grad. student > Chemistry and Physics of Materials Unit > JNCASR > Bangalore , India > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum -- Andrea Dal Corso Tel. 0039-040-3787428 SISSA, Via Bonomea 265 Fax. 0039-040-3787249 I-34136 Trieste (Italy) e-mail: dalcorso at sissa.it
