<html>Dear Christoph,<br /><br />Try to decrease alph_mix to 0.1. Is it enough to converge?<br /><br />Best regards,<br /><br />Antoine Jay<br /><br />On Wednesday, June 27, 2018 14:16 CEST, Christoph Wolf <wolf.christoph@qns.science> wrote:<br /> <blockquote type="cite" cite="CAMC_G_4yjcUUybT3Wt7fnRkU+YA8MA4CgQeS6zsnxXGhYgL5ew@mail.gmail.com"><div dir="ltr">Dear all,<div> </div><div>I have recently encountered an "interesting phenomenon".</div><div> </div><div>Let's say I have determined the (zone boundary phonon frequency) convergence parameter for a unit cell to be a k-grid of 6x6x6 and a ecutwfc=120 Ry. If I now take a 2x2x2 supercell of the material (using the relaxed cell as reference) I (naively) assumed that that would translate to a 3x3x3 k-grid, however I can never manage to converge phonons with that kind of setting as during the initial electric fields calculation the minimization will start to oscillate like this:</div><div> </div><div><div> </div><div> iter # 17 total cpu time : 8249.5 secs <a href="http://av.it">av.it</a>.: 1.8</div><div> thresh= 2.804E-05 alpha_mix = 0.700 |ddv_scf|^2 = 1.396E-07</div><div> </div><div> iter # 18 total cpu time : 8353.6 secs <a href="http://av.it">av.it</a>.: 1.0</div><div> thresh= 3.737E-05 alpha_mix = 0.700 |ddv_scf|^2 = 1.506E-08</div><div> </div><div> iter # 19 total cpu time : 8876.9 secs <a href="http://av.it">av.it</a>.: 15.4</div><div> thresh= 1.227E-05 alpha_mix = 0.700 |ddv_scf|^2 = 6.969E-08</div><div> </div><div> iter # 20 total cpu time : 9303.8 secs <a href="http://av.it">av.it</a>.: 12.1</div><div> thresh= 2.640E-05 alpha_mix = 0.700 |ddv_scf|^2 = 6.076E-08</div><div> </div><div> iter # 21 total cpu time : 9751.4 secs <a href="http://av.it">av.it</a>.: 12.9</div><div> thresh= 2.465E-05 alpha_mix = 0.700 |ddv_scf|^2 = 3.246E-08</div><div> </div><div> iter # 22 total cpu time : 10145.8 secs <a href="http://av.it">av.it</a>.: 11.1</div><div> thresh= 1.802E-05 alpha_mix = 0.700 |ddv_scf|^2 = 3.519E-08</div><div> </div><div> iter # 23 total cpu time : 10542.9 secs <a href="http://av.it">av.it</a>.: 11.2</div><div> thresh= 1.876E-05 alpha_mix = 0.700 |ddv_scf|^2 = 3.168E-09</div></div><div> </div><div> </div><div>Is this a common problem or am I doing something completely wrong...? </div><div> </div><div>Your help is very much appreciated!</div><div> </div><div>Best,</div><div>Chris </div><div> </div><div>--<div class="gmail_signature"><div dir="ltr">Postdoctoral Researcher<br />Center for Quantum Nanoscience, Institute for Basic Science<br />Ewha Womans University, Seoul, South Korea<blockquote type="cite" style="font-size:12.8px"><div dir="ltr"><div><div dir="ltr"> </div></div></div></blockquote></div></div></div></div></blockquote><br /><br /><br /> </html>