[CP2K-user] [CP2K:18257] CP2K exercise for converging the cutoff

[DMT]

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.

Dobromir

On Monday, December 26, 2022 at 10:54:36 AM UTC+2 tkuehne wrote:

> Dear Zhuoran, 
>
> you can find more detailed informations at: 
> 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
>
> Best, 
> Thomas Kühne
>
> Am 19.12.2022 um 06:26 schrieb Dragoon <longdr... 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
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