Dear Vincenzo Verdolino, Same problem here, and this could be version dependent. I tested a system with D3d symmetry. The QE4.3 and QE 5.1 give perfect phonon dispersion, but with QE5.0.x there is always small imaginary frequencies around a high symmetric point (but not Gamma), you may try with latest QE or with some older one (like 4.3). Hope this helps.
On Mon, Aug 25, 2014 at 7:04 PM, Vincenzo Verdolino < vincenzo.verdolino at gmail.com> wrote: > I have personally tested several things...PW cutoff, k sampling fft > mash...everything...the only missing thing is the phonon tr2 value...i am > doing that right now and let you know > > Vincenzo > > Sent from my iPhone > > On 25/ago/2014, at 12:51, "jzlhubei at gmail.com" <jzlhubei at gmail.com> > wrote: > > I have the similar problem with QE calculation with Phonon, I can not > reproduece the result of an article for negative frequency around Gamma. > But I think that the tr2_ph to be 1.0d-14 is enough. > and recently I found Blog talks abount this question for negative > frequency. BUt I can not get the idea why.I hope some senior user can give > insight > comment on this question > the Blog web is http://blog.sina.com.cn/s/blog_5f15ead20101rhyj.html > > ------------------------------ > jzlhubei at gmail.com > > > *From:* Vincenzo Verdolino <vincenzo.verdolino at gmail.com> > *Date:* 2014-08-25 17:05 > *To:* dalcorso <dalcorso at sissa.it>; PWSCF Forum <pw_forum at pwscf.org> > *Subject:* Re: [Pw_forum] Phonon calculation > Hi Andrea, > > > thank you for your answer, i will do that and give you updates if things > get better. > > Vincenzo > > > On Mon, Aug 25, 2014 at 10:40 AM, Andrea Dal Corso <dalcorso at sissa.it> > wrote: > >> I would start checking convergence with respect to tr2_ph. >> >> HTH, >> >> Andrea >> >> >> >> On Mon, 2014-08-25 at 07:25 +0200, Vincenzo Verdolino wrote: >> > _______________________________________________ >> > Pw_forum mailing list >> > Pw_forum at pwscf.org >> > http://pwscf.org/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://pwscf.org/mailman/listinfo/pw_forum >> > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum > -- Xiao-Long Zhang Ph.D student, Institute of Physics, Chinese Academy of Sciences 8 Nansanjie, Zhongguancun Beijing 100190, China Email: xlzhang at iphy.ac.cn OR xlzhang.iop at gmail.com <zgxolg at gmail.com> -------------- next part -------------- An HTML attachment was scrubbed... URL: http://pwscf.org/pipermail/pw_forum/attachments/20140825/ae5cf28e/attachment.html