On Jul 20, 2012, at 7:56 , Koushik Pal wrote: > The system is Sb2Se3 (SG-166). No, the scalar relativistic phonon > calculation > also does not have correct symmetry.
what about the symmetry of the self-consistent calculation? If it is not what you expect, please note the following: http://www.quantum-espresso.org/wp-content/uploads/Doc/pw_user_guide/ node19.html#SECTION000600190000000000000 > I have one more question. Why doesn't the pw.x code give pressure > on the system > in spin-orbit calculation? it does: specify tstress=.true. in &control P. > ------------------------------ > > Message: 7 > Date: Tue, 17 Jul 2012 15:54:12 +0200 > From: Andrea Dal Corso <dalcorso at sissa.it> > Subject: Re: [Pw_forum] anomaly in phonon frequencies as obtained > using DFPT (ph.x) in a spin-orbit calculation > To: PWSCF Forum <pw_forum at pwscf.org> > Message-ID: <1342533252.4490.15.camel at ulisse.cm.sissa.it> > Content-Type: text/plain > > 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 > > > > > ------------------------------ > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > > > End of Pw_forum Digest, Vol 61, Issue 49 > **************************************** > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum --- Paolo Giannozzi, Dept of Chemistry&Physics&Environment, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
