[CP2K-user] bulk cell opt questions

Fabian Ducry fabia... at gmail.com
Mon Apr 27 15:05:03 UTC 2020

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 dependant 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.

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