[CP2K-user] [CP2K:16893] Re: Slow force calculation step timing using hybrid functionals

['Frederick Stein' via cp2k]

Dear Branislav,

If you use the section &XC_SECTION <FUNCTIONAL_NAME>, CP2K will use the 
standard parameters of the HF section. The employed thresholds in the 
SCREENING provide accurate results but can be too tight. It might help, to 
set the respective parameters of HF section explicitly:
&XC
# Add your other subsections here
&HF
&SCREENING
#Choose smaller values for higher accuracy
EPS_SCHWARZ 1.0E-6
EPS_SCHWARZ_FORCES 1.0E-5
&END SCREENING
&END HF
&END XC

Another parameter to tune is EPS_DEFAULT in the QS section.

Consult also the CP2K manual 
(https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/DFT/XC/HF.html) for 
further reference.

HTH

Frederick

dr.bra... at gmail.com schrieb am Dienstag, 26. April 2022 um 16:10:34 UTC+2:

> Dear CP2K users,
>
> I'm experiencing problems when using hybrid functionals such as B3LYP or 
> M062X and while optimizing simple test system (hydrogen bonded acetic acid 
> dimer).
>
> SCF convergence appears to be fast and normal but the Force calculation 
> step is extremely slow. Maybe I made some mistake in the input file?
>
> I attached my input files and output file (B3LYP).
> Also, I don't really understand the timings at the end output file.
>
> Thanks in advance!
> Branislav
>

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