[CP2K-user] [CP2K:20391] Re: Different ways to run PBE50?

[Mikhayla Clothier]

Dear Frederick,

Thank you so much for your response! I'll set it manually from here on out. 

Mikhayla Clothier

On Friday, June 28, 2024 at 12:54:29 PM UTC-4 Frederick Stein wrote:

Dear Mikhayla,
The first approach is correct. But you can make the second approach running 
by adding the HF section. The LibXC-related sections only affect the DFT 
part, not the HF part. It is always up to you to set it up because 
different systems require different setups regarding EPS_SCHWARZ, 
EPS_SCHWARZ_FORCES, MAX_MEMORY, CUTOFF_RADIUS etc.
HTH,
Frederick

Mikhayla Clothier schrieb am Freitag, 28. Juni 2024 um 18:23:26 UTC+2:

Hello,

I would like to use the PBE50 functional. I followed the tutorial provided 
on the website (https://www.cp2k.org/exercises:2017_uzh_cp2k-tutorial:hybrid) 
where the PBE50 functional is created by manually tuning the PBE and HF 
contributions,

    &XC
        &XC_FUNCTIONAL
            &PBE
                SCALE_X 0.50
                SCALE_C 1.0
            &END PBE
        &END XC_FUNCTIONAL
        &HF
            FRACTION 0.50
        &END HF
    &END XC

However, within the manual, there seems to be a separate way to call the 
PBE50 functional from the LibXC library by simply saying 

    &XC
        &XC_FUNCTIONAL
            &HYB_GGA_XC_PBE50
            &END HYB_GGA_XC_PBE50
        &END XC_FUNCTIONAL
    &END XC

without the need to manually specify the HF contribution. I ran both 
approaches with a single water molecule to compare, and I got different 
energies. Also, just using the HYB_GGA_XC_PBE50 approach did not result in 
the "Hartree Fock exchange energy" being printed in the output.

Which method is the correct approach? If its the first, how does the 
HYB_GGA_XC_PBE50 functional work?  I am using the 2022.1 version of CP2K 
with the 4.1.4 version of OpenMPI.

I've attached the output files to this post. The one for manually setting 
PBE50 is named 
"water_manual.out" and the one where I just set the functional as 
HYB_GGA_XC_PBE50 is called "water_hyb.out." If I need to upload my input 
files as well, please let me know!

Thank you!

Mikhayla Clothier

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