[CP2K-user] [CP2K:18255] CP2K exercise for converging the cutoff

[Thomas Kühne]

Dear Zhuoran, 

you can find more detailed informations at: https://www.cp2k.org/howto:converging_cutoff <https://www.cp2k.org/howto:converging_cutoff>
A very rough a priori estimate for the cutoff can be found at: https://www.cp2k.org/faq:cutoff <https://www.cp2k.org/faq:cutoff>

Best, 
Thomas Kühne

> Am 19.12.2022 um 06:26 schrieb Dragoon <longdragoonae at gmail.com>:
> 
> Hi all,
> 
> 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 https://www.cp2k.org/events:2018_summer_school:converging_cutoff ). This system has 32 H2O, using PBE functional (no XC smoothing) and MOLOPT-SR basis. REL_CUTOFF is 60 Ry.
> 
> 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. <Screenshot from 2022-12-19 00-01-47.png>
> 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.
> I really appreciate any explanations and helps.
> 
> Zhuoran
> 
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> <Screenshot from 2022-12-19 00-01-47.png>



==============================
Thomas D. Kühne
Dynamics of Condensed Matter
Chair of Theoretical Chemistry
University of Paderborn
Warburger Str. 100
D-33098 Paderborn
Germany
thomas.kuehne at upb.de
+49/(0)5251/60-5726

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