[CP2K-user] Hybdrid functionals

[Frederick Stein]

Hi Mikael,

Probably, you are missing the Hartree-Fock section in the XC section (&HF) 
as CP2K does not set up Hartree-Fock sections of LibXC functionals 
automatically.
If you would like to use the PBE implementation of CP2K, use the PBE 
section in the XC_FUNCTIONAL section, for LibXC you have to set &LIBXC with 
FUNCTIONAL GGA_XC_PBE.

Best,
Frederick

mi... at gmail.com schrieb am Freitag, 4. Juni 2021 um 15:25:35 UTC+2:

> Hi community
>
> I do DFT simulations of polyethylene (PE). PE has a wide band gap (~8.8 
> eV) but with most xc funtionals the band gap is calculated to 6-7 eV.
>
> We have seen that hybrid functionals like HSE03, HSE06 and PBE0 give quite 
> good values (7.97-8.75 eV) plane wave DFT
> https://aip.scitation.org/doi/full/10.1063/1.4983650
> However, when I try these functionals at DFT-GAPW level in CP2K (using 
> libxc) I get band gaps in the order of 4.8-5.3 eV for a small amorphous 
> system. 
>
> Is there some studies done with DFT-GAPW and hybrid functionals?
>
> I use version 8.1 of cp2k.
>
> In the input file I adress libxc functionals as in the HSE06 example below
>      &XC_FUNCTIONAL
>           &LIBXC
>     FUNCTIONAL HYB_GGA_XC_HSE06 
>           &END LIBXC     
>       &END XC_FUNCTIONAL
> is this the correct way?
>
>
> In the manual of 8.0 it is mentioned that PBE0 should be possible to
> use but the PBE0 keyword can not recognized by cp2k.
>
> https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/XC/XC_FUNCTIONAL.html
> Would it be any difference in using PBE0 via keyord to XC_functional 
> compared to using libxc version of PBE0?
>
> Regards,
> Mikael
>
>
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