Dear Christoph, Try to decrease alph_mix to 0.1. Is it enough to converge?
Best regards, Antoine Jay On Wednesday, June 27, 2018 14:16 CEST, Christoph Wolf <[email protected]> wrote: Dear all, I have recently encountered an "interesting phenomenon". 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: iter # 17 total cpu time : 8249.5 secs av.it.: 1.8 thresh= 2.804E-05 alpha_mix = 0.700 |ddv_scf|^2 = 1.396E-07 iter # 18 total cpu time : 8353.6 secs av.it.: 1.0 thresh= 3.737E-05 alpha_mix = 0.700 |ddv_scf|^2 = 1.506E-08 iter # 19 total cpu time : 8876.9 secs av.it.: 15.4 thresh= 1.227E-05 alpha_mix = 0.700 |ddv_scf|^2 = 6.969E-08 iter # 20 total cpu time : 9303.8 secs av.it.: 12.1 thresh= 2.640E-05 alpha_mix = 0.700 |ddv_scf|^2 = 6.076E-08 iter # 21 total cpu time : 9751.4 secs av.it.: 12.9 thresh= 2.465E-05 alpha_mix = 0.700 |ddv_scf|^2 = 3.246E-08 iter # 22 total cpu time : 10145.8 secs av.it.: 11.1 thresh= 1.802E-05 alpha_mix = 0.700 |ddv_scf|^2 = 3.519E-08 iter # 23 total cpu time : 10542.9 secs av.it.: 11.2 thresh= 1.876E-05 alpha_mix = 0.700 |ddv_scf|^2 = 3.168E-09 Is this a common problem or am I doing something completely wrong...? Your help is very much appreciated! Best,Chris --Postdoctoral Researcher Center for Quantum Nanoscience, Institute for Basic Science Ewha Womans University, Seoul, South Korea
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