Recommended value for HFRCUT

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Michael.Sluydts
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Recommended value for HFRCUT

#1 Post by Michael.Sluydts » Mon Apr 19, 2021 7:25 pm

For hybrid XC functionals with a finite band gap, HFRCUT = - 1 is recommended on the wiki (wiki/index.php/HFRCUT). However, we do not find any recommendations for this tag in any explanation or examples of hybrid XC functionals on the wiki (e.g. Si HSE band structure example, which has a band gap 1.12eV wiki/index.php/Si_HSE_bandstructure). Only in the explanation of RPA calculations it's mentioned because HF calculations are done in the second step. Also in the literature does not always seem to be used for semiconductors or insulators.
For HSE06 calculations on CsPbI3 there is a big change in band gap if we change HFRCUT from 0 to -1 (band gap changes from 2.3 to 2.9 eV). The literature only mentions the 2.3 eV value.

Are we correct in assuming the -1 value is more correct? What usage do you recommend?

used INCAR:
PREC=Normal
ALGO=Normal
LREAL=.FALSE.
LWAVE=.FALSE.
LORBIT=11
ISMEAR=0
LASPH=.TRUE.
EDIFF=1e-05
ENCUT=600
SIGMA=0.05
LCHARG=.FALSE.
ISPIN=1
IVDW=0
NCORE=1
LHFCALC=.TRUE.
HFSCREEN=0.2
PRECFOCK=FAST
NKRED=1
HFRCUT=-1

ferenc_karsai
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Re: Recommended value for HFRCUT

#2 Post by ferenc_karsai » Tue Apr 27, 2021 8:33 am

HFRCUT=0 and HFRCUT=-1 should converge to the same results with respect to k-mesh.
So please try increasing the k-mesh in your calculation.

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Re: Recommended value for HFRCUT

#3 Post by ferenc_karsai » Fri Apr 30, 2021 10:04 am

The wiki entry has also been updated:
wiki/index.php/HFRCUT

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