In many publications a CUTOFF of 400 is normal and acceptable. I haven't seen anyone to have to go beyond 600, so far. Also, a very good value for NGRIDS is 5.<div><br></div><div>Dobromir<br><br></div><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Monday, December 26, 2022 at 10:54:36 AM UTC+2 tkuehne wrote:<br/></div><blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><div style="word-wrap:break-word;line-break:after-white-space">Dear Zhuoran, <div><br></div><div>you can find more detailed informations at: <a href="https://www.cp2k.org/howto:converging_cutoff" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=en&q=https://www.cp2k.org/howto:converging_cutoff&source=gmail&ust=1672132052720000&usg=AOvVaw2usiSdfwaWldY7d2WjI-Xp">https://www.cp2k.org/howto:converging_cutoff</a></div><div>A very rough a priori estimate for the cutoff can be found at: <a href="https://www.cp2k.org/faq:cutoff" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=en&q=https://www.cp2k.org/faq:cutoff&source=gmail&ust=1672132052720000&usg=AOvVaw12AiA6g7WrQ8qe99BCEeAJ">https://www.cp2k.org/faq:cutoff</a></div><div><br></div><div>Best, </div><div>Thomas Kühne<br><div><br><blockquote type="cite"></blockquote></div></div></div><div style="word-wrap:break-word;line-break:after-white-space"><div><div><blockquote type="cite"><div>Am 19.12.2022 um 06:26 schrieb Dragoon <<a href data-email-masked rel="nofollow">longdr...@gmail.com</a>>:</div><br></blockquote></div></div></div><div style="word-wrap:break-word;line-break:after-white-space"><div><div><blockquote type="cite"><div>Hi all,<div><br></div><div>As I'm still struggling with converging the plane wave cutoff, I tried this CP2K exercise for converging the cutoff for a water system (the link is <a href="https://www.cp2k.org/events:2018_summer_school:converging_cutoff" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=en&q=https://www.cp2k.org/events:2018_summer_school:converging_cutoff&source=gmail&ust=1672132052720000&usg=AOvVaw2xcd4DspOBqR5WLd2ysQfm">https://www.cp2k.org/events:2018_summer_school:converging_cutoff</a> ). This system has 32 H2O, using PBE functional (no XC smoothing) and MOLOPT-SR basis. REL_CUTOFF is 60 Ry.</div><div><br></div></div></blockquote></div></div></div><div style="word-wrap:break-word;line-break:after-white-space"><div><div><blockquote type="cite"><div><div>I ran this exercise, and extended the cutoff to 2000Ry, yet I'm not sure at which cutoff either the energy or force is converged. I attached the result below. <span><Screenshot from 2022-12-19 00-01-47.png></span></div></div></blockquote></div></div></div><div style="word-wrap:break-word;line-break:after-white-space"><div><div><blockquote type="cite"><div><div>I do notice that the most coarse grid (#4) has the most grid levels starting from 800 Ry. I guess that means the cutoff is probably already too high, and that might be related to a slow convergence. Yet I'm not sure how to improve that, nor further explain this behavior for this simple system.</div><div>I really appreciate any explanations and helps.</div><div><br></div><div>Zhuoran</div><div><br></div></div></blockquote></div></div></div><div style="word-wrap:break-word;line-break:after-white-space"><div><div><blockquote type="cite"><div>
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