[CP2K-user] The cutoff unit in CP2K

[Marcella Iannuzzi]

In GPW the electron density, and not the wave functions, is expanded in PW.
Therefore the PW cutoff is four time as large as a the one you would use to 
expand the wave functions, as it is done in Quantum ESPRESSO.
Whether or not the grids and PW parts of one GPW calculation become 
expensive and dominant depends on the system and on the method you are 
using. Hence increasing the PW cutoff, within a reasonable range, is often 
not too problematic.
Regards
Marcella

On Saturday, January 16, 2021 at 8:46:10 AM UTC+1 msha... at gmail.com 
wrote:

> Hello everyone,
>
> I wanted to ask a question about the cutoff value unit. The unit in the 
> manual is in Ry and the default value is 280 Ry and for some systems, we 
> may need to increase this value. I wanted to know why would we need such 
> huge values? In Quantum ESPRESSO 60-80 Ry is fine for some calculations and 
> adopting higher values is computationally expensive. Can you please explain 
> a bit more about the unit of the cutoff in CP2K? and why in CP2K a larger 
> value is required than QE?
>
> Thank you very much in advance.
>
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