PRECFOCK

PRECFOCK = Low | Medium | Fast | Normal | Accurate
Default: PRECFOCK = Normal 

Description: PRECFOCK controls the FFT grids used in the exact exchange routines (Hartree-Fock and hybrid functionals).

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PRECFOCK	FFT-grid	Augmentation charge	Quality
Low	Gcut	identical to standard DFT	large noise in forces/energy errors
Medium	identical to std. FFT	identical to standard DFT	some noise in forces/good energy
Fast	Gcut	very soft augmentation chargea	some noise in forces/good energy
Normal	3/2×Gcut	soft augmentation chargeb	accurate forces and energy
Accurate	2×Gcut	soft augmentation chargeb	very accurate forces and energy
a soft augmentation charge: radius for augmentation sphere is increased by factor 1.25 compared to default. b very soft augmentation charge: radius is increased by factor 1.35 compared to default except for s-like charge, for the s-channel the radius of the augmentation sphere is increased by a factor 1.25.

where

$E_{\rm cut}=\frac{\hbar^2}{2m_e}G_{\rm cut}^2$

with E_cut=ENCUT.

Related Tags and Sections

ENCUT, hybrid functionals, settings for specific hybrid functionals

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