[Pw_forum] Phonon calculation

[Xiaolong Zhang]

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:
>> > _______________________________________________
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>>
>> --
>> 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
>>
>>
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>
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-- 
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>
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