Hi Dobromir and Thomas,<div><br></div><div>Thank you all for the replies. </div><div>As I dug through the threads in this group. I realized many problems of the CP2k <a href="https://www.cp2k.org/howto:converging_cutoff">Howto</a> and <a href="https://www.cp2k.org/events:2018_summer_school:converging_cutoff">exercise</a> about PW cutoff. Please correct me for my misunderstandings. </div><div>1. Based on one previous <a href="https://groups.google.com/g/cp2k/c/ySUAYEgwmhc/">discussion</a>, SCF needs to be converged with a large enough REL_CUTOFF, instead of a 1 step calculation like in the Howto. </div><div>2. EPS_PGF_ORB 1.0E-07 or lower is usually needed for converging SCF.</div><div>3. 1e-3 ev / 3e-5 Hartree energy convergence is good enough for most system? For this convergence the exercise system need to go to 800 Ry cutoff.</div><div>4. GAPW sometimes can achieve a much smaller cutoff than GPW method. The default parameters in CP2k are good enough for GAPW.</div><div><br></div><div>Thank you again,</div><div>Zhuoran </div><div><br></div><div><br></div><div><br><br></div><div class="gmail_quote"><div dir="auto" class="gmail_attr">在2022年12月26日星期一 UTC-5 04:12:08<DMT> 写道：<br/></div><blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">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" rel="nofollow" target="_blank" data-saferedirecturl="https://www.google.com/url?hl=zh-CN&q=https://www.cp2k.org/howto:converging_cutoff&source=gmail&ust=1672157606165000&usg=AOvVaw2moCeC7oLxytwm1JKIC9kf">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" rel="nofollow" target="_blank" data-saferedirecturl="https://www.google.com/url?hl=zh-CN&q=https://www.cp2k.org/faq:cutoff&source=gmail&ust=1672157606165000&usg=AOvVaw0ympP7qr4wFdbfuVs9NYNh">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 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" rel="nofollow" target="_blank" data-saferedirecturl="https://www.google.com/url?hl=zh-CN&q=https://www.cp2k.org/events:2018_summer_school:converging_cutoff&source=gmail&ust=1672157606165000&usg=AOvVaw3-QPUyiplHBxIhrnxtpI-O">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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