[CP2K-user] Hybdrid functionals

[Mikael Unge]

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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