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<div dir="ltr">Dear L,</div><div dir="ltr"><br clear="none"></div><div dir="ltr">I understand what you're writing that <span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;">DFPT allows you to simulate a monochromatic perturbation of any periodicity with a unit cell (learned from the tutorial), but for<span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"> frozen phonon, I have no idea yet and need to study more about its basics.</span></span></span></span></div><div dir="ltr"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><br clear="none"></span></span></span></span></div><div dir="ltr"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;">For short, does it mean for <span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;">DFPT→1 unit cell is ok, </span></span></span></span></span></span></div><div dir="ltr"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;">and frozen phonon→need supercell?</span></span></span></span></span></span></div><div dir="ltr"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><br clear="none"></span></span></span></span></span></span></div><div dir="ltr"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><br clear="none"></span></span></span></span></span></span></div><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) ? </font></div><div dir="ltr"><font color="#26282a"><br clear="none"></font></div><div dir="ltr"><font color="#26282a"><br clear="none"></font></div><div dir="ltr"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span 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><div dir="ltr"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><br clear="none"></span></span></span></span></span></span></span></div><div dir="ltr"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span>HY Lu</span><br clear="none"></span></span></span></span></span></span></div><div dir="ltr"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><br clear="none"></span></span></span></span></span></span></div><div dir="ltr"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><br clear="none"></span></span></span></span></span></span></div><div dir="ltr"><span><span style="color:rgb(38, 40, 42);font-family:Helvetica Neue, Helvetica, Arial, sans-serif;"><br clear="none"></span></span></div><div dir="ltr"><br clear="none"></div><div><br clear="none"></div>
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在 2023年11月15日 星期三 下午03:56:04 [GMT+8]， Lorenzo Paulatto<lorenzo.paulatto@cnrs.fr> 寫道：
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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" rel="nofollow" target="_blank">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>
<div id="ydpc3882935yiv4157248105ydp4a30c316yiv6277712289yqtfd73628" class="ydpc3882935yiv4157248105ydp4a30c316yiv6277712289yqt3049127918"><p>L<br clear="none">
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