<div dir="ltr"><div>Dear <span style="font-size:13px;font-family:arial,sans-serif;font-weight:bold;white-space:nowrap">Vincenzo Verdolino,</span></div><div><span style="font-size:13px;font-family:arial,sans-serif;font-weight:bold;white-space:nowrap"><br>
</span></div><div>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</div><div>dispersion, but with QE5.0.x there is always small imaginary frequencies around a high symmetric point (but not Gamma), you may try with</div>
<div>latest QE or with some older one (like 4.3). Hope this helps.</div><div><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Mon, Aug 25, 2014 at 7:04 PM, Vincenzo Verdolino <span dir="ltr"><<a href="mailto:vincenzo.verdolino@gmail.com" target="_blank">vincenzo.verdolino@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="auto"><div>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</div>
<div><br></div><div>Vincenzo<br><br>Sent from my iPhone</div><div><div class="h5"><div><br>On 25/ago/2014, at 12:51, "<a href="mailto:jzlhubei@gmail.com" target="_blank">jzlhubei@gmail.com</a>" <<a href="mailto:jzlhubei@gmail.com" target="_blank">jzlhubei@gmail.com</a>> wrote:<br>
<br></div><blockquote type="cite"><div>
<div><span></span>I have the similar problem with QE calculation with Phonon, I can not reproduece the result of an article for negative frequency around Gamma.</div><div>But I think that the tr2_ph to be <span style="font-family:宋体,Tahoma;font-size:14.399999618530273px;line-height:normal;background-color:window">1.0d-14 is enough.</span></div>
<div><span style="font-size:10.5pt;line-height:1.5;background-color:window">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</span></div>
<div><span style="font-size:10.5pt;line-height:1.5;background-color:window">comment on this question</span></div><div><span style="font-size:10.5pt;line-height:1.5;background-color:window">the Blog web is </span><span style="background-color:window;font-size:10.5pt;line-height:1.5"><a href="http://blog.sina.com.cn/s/blog_5f15ead20101rhyj.html" target="_blank">http://blog.sina.com.cn/s/blog_5f15ead20101rhyj.html</a></span></div>
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<div><span><div style="MARGIN:10px;FONT-FAMILY:verdana;FONT-SIZE:10pt"><div><a href="mailto:jzlhubei@gmail.com" target="_blank">jzlhubei@gmail.com</a></div></div></span></div>
<blockquote style="margin-top:0px;margin-bottom:0px;margin-left:0.5em"><div> </div><div style="border:none;border-top:solid #b5c4df 1.0pt;padding:3.0pt 0cm 0cm 0cm"><div style="PADDING-RIGHT:8px;PADDING-LEFT:8px;FONT-SIZE:12px;FONT-FAMILY:tahoma;COLOR:#000000;BACKGROUND:#efefef;PADDING-BOTTOM:8px;PADDING-TOP:8px">
<div><b>From:</b> <a href="mailto:vincenzo.verdolino@gmail.com" target="_blank">Vincenzo Verdolino</a></div><div><b>Date:</b> 2014-08-25 17:05</div><div><b>To:</b> <a href="mailto:dalcorso@sissa.it" target="_blank">dalcorso</a>; <a href="mailto:pw_forum@pwscf.org" target="_blank">PWSCF Forum</a></div>
<div><b>Subject:</b> Re: [Pw_forum] Phonon calculation</div></div></div><div><div><div dir="ltr">Hi Andrea,<div><br></div><div><br></div><div>thank you for your answer, i will do that and give you updates if things get better.</div>
<div><br></div><div>Vincenzo </div></div><div class="gmail_extra"><br><br>
<div class="gmail_quote">On Mon, Aug 25, 2014 at 10:40 AM, Andrea Dal Corso <span dir="ltr"><<a href="mailto:dalcorso@sissa.it" target="_blank">dalcorso@sissa.it</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
I would start checking convergence with respect to tr2_ph.<br>
<br>
HTH,<br>
<br>
Andrea<br>
<br>
<br>
<br>
On Mon, 2014-08-25 at 07:25 +0200, Vincenzo Verdolino wrote:<br>
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