PRECFOCK: Difference between revisions
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Description: {{TAG|PRECFOCK}} controls the FFT grids used in the exact exchange routines (Hartree-Fock and hybrid functionals). | Description: {{TAG|PRECFOCK}} controls the FFT grids used in the exact exchange routines (Hartree-Fock and hybrid functionals). | ||
---- | ---- | ||
:{| cellpadding="5" cellspacing="0" border="1" | |||
|{{TAG|PRECFOCK}} || FFT-grid || Augmentation charge || Quality | |{{TAG|PRECFOCK}} || FFT-grid || Augmentation charge || Quality | ||
|- | |- | ||
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| Medium || identical to std. FFT || identical to standard DFT || some noise in forces/good energy | | Medium || identical to std. FFT || identical to standard DFT || some noise in forces/good energy | ||
|- | |- | ||
| Fast || G<sub>cut</sub> || very soft augmentation charge || some noise in forces/good energy | | Fast || G<sub>cut</sub> || very soft augmentation charge<sup>a</sup>|| some noise in forces/good energy | ||
|- | |- | ||
| Normal || 3/2×G<sub>cut</sub> || soft augmentation charge || accurate forces and energy | | Normal || 3/2×G<sub>cut</sub> || soft augmentation charge<sup>b</sup> || accurate forces and energy | ||
|- | |- | ||
| Accurate || 2×G<sub>cut</sub> || soft augmentation charge || very accurate forces and energy | | Accurate || 2×G<sub>cut</sub> || soft augmentation charge<sup>b</sup> || very accurate forces and energy | ||
|- | |||
|colspan="4"|<sup>a</sup > soft augmentation charge: radius for augmentation sphere is increased by factor 1.25 compared to default. | |||
<sup>b</sup> 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 | |||
:<math>E_{\rm cut}=\frac{\hbar^2}{2m_e}G_{\rm cut}^2</math> | |||
with E<sub>cut</sub>={{TAG|ENCUT}}. | |||
== Related Tags and Sections == | == Related Tags and Sections == | ||
Revision as of 13:22, 15 February 2011
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).
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
with Ecut=ENCUT.
Related Tags and Sections
ENCUT, hybrid functionals, settings for specific hybrid functionals