[CP2K-user] bulk cell opt questions

Jing Liu liujin... at gmail.com
Tue Apr 28 10:55:43 UTC 2020

Dear Fabian

Thank you for your suggestions, I'm running new tests based on them and 
hopefully the charge inaccuracy can be solved...

As for the basis set, I agree that they should not be directly compared 
since different basis set of course yield different total energy, however I 
expect somewhat "smaller" difference, not few hundred hartree... With this 
much of difference I can only assume one of the calclation is completely 

Best regards

Liu Jing

在 2020年4月27日星期一 UTC+2下午5:05:03,Fabian Ducry写道:
> Dear Jing,
> Some pointers to improve your simulations:
>  - The charge you find is an artefact of the numerical inaccuracy in your 
> system. EPS_DEFAULT should be tighter, just leave it at the default value 
> of 1.0E-10
>  - How did you choose CUTOFF and REL_CUTOFF, did you follow 
> https://www.cp2k.org/howto:converging_cutoff? For CELL_OPT you might need 
> to increase these numbers
>  - SZV is a very small basis set, useful for testing but not for anything 
> else. DZVP often produces okish results but not always. You should check 
> the convergence of the basis set.
> The total energy is very much dependent on the basis set that you use. So 
> you cannot compare the energy of your "reference" with the one from cp2k 
> and expect them to be the same.
> Best,
> Fabian
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