[CP2K-user] [CP2K:22006] Wavelet Poisson solver - Huge change in total energy when increasing the plane-wave cut-off energy from 1200 to 1260 Ry

[Torstein Fjermestad]

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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