[CP2K-user] [CP2K:22008] Re: Wavelet Poisson solver - Huge change in total energy when increasing the plane-wave cut-off energy from 1200 to 1260 Ry

[Frederick Stein]

Dear Torstein,
You not only need to adjust the CUTOFF but also EPS_DEFAULT (and if set 
explicitly the other thresholds) in the QS section. How did you obtain the 
input file? I would never set all parameters. Especially EPS_DEFAULT sets a 
variety of other parameters if these are not set explicitly.
Best,
Frederick

Torstein Fjermestad schrieb am Montag, 22. Dezember 2025 um 20:09:02 UTC+1:

> Dear all, 
>
> As part of a basis set convergence test, I gradually increase the plane 
> wave basis set cut-off energy. The atomic system is a cluster model of 
> methanol adsorbed in a zeolite. I isolate the system from its neighboring 
> unit cells by using the wavelet Poisson solver. 
> I use a cubic box of 30 Å. The size of the system is about 21 Å in the 
> longest direction. The atom-centered basis set is TZV2P. 
> When I increase the cut-off from 900 Ry to 1200 Ry, the total energy 
> varies in a range less than 5 kJ/mol. However, when I increase the cut-off 
> from 1200 Ry to 1260 Ry, the total energy is after  6 SCF iterations  
> 1.38E+07 kJ/mol lower! 
> Because of the massively different total energy, I stopped the 
> calculation.   
>
> I have attached the output files of the two calculations. The complete 
> input can be found at the start of the output files. 
>
> What could be the cause of this behavior? 
>
> Thank you very much for your help. 
> Please tell me if you need more information to understand the problem 
> better.
>
> Best regards,
> Torstein Fjermestad
>  
>

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