<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Dear Arini,<div class=""><br class=""></div><div class="">As a final remark, this is what experience tells us, but remember that proper testing should be directly performed on the desired property with a desired accuracy.</div><div class="">This means that a better practice could be e.g. to test ``ecutfock`` on phonon frequencies at Gamma (i.e. only displacements in UNITCELL). This already gives a better idea of convergence, while still not going for expensive supercells.</div><div class=""><br class=""></div><div class="">If you are interested in more details, I’d suggest you the following paper, which I found particularly instructive: <a href="https://www.nature.com/articles/s41524-018-0127-2" class="">https://www.nature.com/articles/s41524-018-0127-2</a></div><div class=""><br class=""></div><div class="">Bests,</div><div class="">Lorenzo</div><div class=""><br class=""></div><div class=""><div class="">
<meta charset="UTF-8" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div><div class="">********************************</div><div class="">Lorenzo Bastonero</div><div class=""><br class=""></div><div class="">PhD Student</div><div class="">U Bremen Excellence Chair,<br class="">Bremen Center for Computational Materials Science,<br class="">and MAPEX Center for Materials and Processes</div><div class=""><br class=""></div><div class="">University of Bremen</div><div class="">Faculty of Production Engineering</div><div class="">TAB-Building, Room 3.32</div><div class="">Am Fallturm 1</div><div class="">28359 Bremen, DE</div><br class="Apple-interchange-newline"><a href="http://www.hmi.uni-bremen.de/" class="">http://www.hmi.uni-bremen.de/</a></div></div></div></div></div></div>
</div>
<div><br class=""><blockquote type="cite" class=""><div class="">Il giorno 12 apr 2023, alle ore 14:08, Arini Kar <<a href="mailto:16i170008@iitb.ac.in" class="">16i170008@iitb.ac.in</a>> ha scritto:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" class=""><div style="font-size: 10pt; font-family: Verdana,Geneva,sans-serif" class=""><p class="">Dear Lorenzo,</p><p class="">Your suggestion was helpful. The forces on the pristine unit cell did not change after reducing ecutfock to 2*ecutwfc. Thanks a lot.</p><p class=""><br class=""></p><p class="">Regards<br class="">Arini</p>
<div id="signature" class=""></div><p class=""><br class=""></p><p id="reply-intro" class="">On 2023-04-12 13:26, Lorenzo Bastonero wrote:</p>
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0" class="">
<div id="replybody1" class="">
<div dir="auto" class="">Dear Arini,
<div class=""> </div>
<div class="">You should do some test first in the pristine unit cell structure before going forward to the supercell calculations. </div>
<div class=""> </div>
<div class="">In principle, you could lower down even more that cutoff (and the qpoint for the fock operator as well). Usually a good threshold is ~10^-5 Ry/bohr on every atomic force component.</div>
<div class=""> </div>
<div class="">Note: this threshold is different from the one of the relax. So you should check that when changing your variables (ecutfock in this case) all your forces don't change within this threshold.</div>
<div class=""> </div>
<div class="">HTH,</div>
<div class="">Lorenzo <br class=""><br class="">
<div dir="ltr" class="">Inviato da iPhone</div>
<div dir="ltr" class=""><br class="">
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0" class="">Il giorno 11 apr 2023, alle ore 20:45, Arini Kar via users <<a href="mailto:users@lists.quantum-espresso.org" class="">users@lists.quantum-espresso.org</a>> ha scritto:<br class=""><br class=""></blockquote>
</div>
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0" class="">
<div dir="ltr" class=""><p class="">Dear users,</p><p class="">I am trying to run phonon calculations using phonopy. I am using norm conserving pseudopotential. Can I use ecutfock = 2*ecutwfc instead of the default value in the scf calculations? Would it affect the accuracy of force calculations?</p><p class="">Thanking you.</p><p class="">Regards</p><p class="">Arini Kar</p><p class="">PhD student </p><p class="">Indian Institute of Technology Bombay, India</p><p class=""><br class=""></p>
<span class="">_______________________________________________</span><br class=""><span class="">The Quantum ESPRESSO community stands by the Ukrainian</span><br class=""><span class="">people and expresses its concerns about the devastating</span><br class=""><span class="">effects that the Russian military offensive has on their</span><br class=""><span class="">country and on the free and peaceful scientific, cultural,</span><br class=""><span class="">and economic cooperation amongst peoples</span><br class=""><span class="">_______________________________________________</span><br class=""><span class="">Quantum ESPRESSO is supported by MaX (<a href="http://www.max-centre.eu" class="">www.max-centre.eu</a>)</span><br class=""><span class="">users mailing list <a href="mailto:users@lists.quantum-espresso.org" class="">users@lists.quantum-espresso.org</a></span><br class=""><span class=""><a href="https://lists.quantum-espresso.org/mailman/listinfo/users" class="">https://lists.quantum-espresso.org/mailman/listinfo/users</a></span></div>
</blockquote>
</div>
</div>
</div>
</blockquote>
</div>
</div></blockquote></div><br class=""></div></body></html>