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<div dir="ltr"><font color="#26282a">Sorry but for 1 more
naive question, if I use 2 unit cell instead of 1 in
DFPT, would it be expected to have difference between
the two cases ( only at Gamma point) ? <br>
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<p>yes, it is different. Because you would get twice as many
phonons, but half of them would be periodic inside the supercell
(and correspond to Gamma) the other would not be (and correspond
to a zone-border q-point).</p>
<p>hth<br>
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style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span>Best
Regards, </span></span></span></span></span></span></span></div>
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<div> 在 2023年11月15日 星期三 下午03:56:04 [GMT+8]， Lorenzo
Paulatto<a class="moz-txt-link-rfc2396E" href="mailto:lorenzo.paulatto@cnrs.fr"><lorenzo.paulatto@cnrs.fr></a> 寫道： </div>
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<div
class="ydpc3882935yiv4157248105ydp4a30c316yiv6277712289moz-cite-prefix">On
15/11/2023 08:45, <a shape="rect"
href="mailto:ludwigboltzmann.sc10@nycu.edu.tw"
class="ydpc3882935yiv4157248105ydp4a30c316yiv6277712289moz-txt-link-abbreviated moz-txt-link-freetext"
rel="nofollow" target="_blank" moz-do-not-send="true">ludwigboltzmann.sc10@nycu.edu.tw</a>
wrote:<br clear="none">
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<div dir="ltr"> Hope this will give you an idea why such<b>
symmetry reduced</b> supercell calculation is being
carried out.</div>
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<p>The idea is "symmetry reduced".</p>
<p>I.e. DFPT allows you to simulate a monochromatic
perturbation of any periodicity with a unit cell, while
frozen phonon can only simulate perturbation which have
the periodicity of the cell you are using. But to break
symmetry, you need a supercell.<br clear="none">
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<p>kind regards</p>
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<pre class="moz-quote-pre" wrap="">_______________________________________________
The Quantum ESPRESSO community stands by the Ukrainian
people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
_______________________________________________
Quantum ESPRESSO is supported by MaX (<a class="moz-txt-link-abbreviated" href="http://www.max-centre.eu">www.max-centre.eu</a>)
users mailing list <a class="moz-txt-link-abbreviated" href="mailto:users@lists.quantum-espresso.org">users@lists.quantum-espresso.org</a>
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<div class="moz-signature">-- <br>
<small>Dr. Lorenzo Paulatto<br>
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université<br>
phone: +33 (0)1 442 79822 / skype: paulatz<br>
<a href="http://www.impmc.upmc.fr/~paulatto/"
class="moz-txt-link-freetext">http://www.impmc.upmc.fr/~paulatto/</a>
- <a href="https://anharmonic.github.io/"
class="moz-txt-link-freetext">https://anharmonic.github.io/</a><br>
23-24/423 B115, 4 place Jussieu 75252 Paris CX 05<small></small></small></div>
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