===== How can one guess a reasonable cutoff value? =====
**This is for the impatient CP2K user:** As a rule of thumb one can multiply the largest exponent of the Gaussian basis sets employed by **40** to obtain a reasonable guess for the cutoff value in Rydberg. The first column of the CP2K basis set format contains the Gaussian exponents, e.g. for the oxygen DZVP-MOLOPT-SR-GTH basis set you may find a value of about 10.4 and the corresponding hydrogen DZVP-MOLOPT-SR-GTH basis set employs a largest exponent of about 10.0. Thus a cutoff value of **10*40 = 400 Rydberg** would be a reasonable guess for a cutoff value to start with. The following values
<code>
Total charge density on r-space grids:        0.0000000000
Total charge density g-space grids:           0.0000000000
</code>
in the CP2K output should be smaller than 10<sup>-8</sup>. Use the PRINT_LEVEL medium
<code>
&GLOBAL
 PRINT_LEVEL medium
 ...
&END GLOBAL
</code>
to get this printout after each SCF iteration step. The default is to print this information when the SCF iteration is converged which possibly might never happen with a too small cutoff value.

For a more fine-tuned setting of the cutoff and the relative cutoff value you may check the this [[howto:converging_cutoff|How-to]].