ENCUTFOCK: Difference between revisions

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Default: none
Default: none
Description: The {{TAG|ENCUTFOCK}} tag sets the energy cutoff that determines the FFT grids used by the Hartree-Fock routines.
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The flag {{TAG|ENCUTFOCK}} is no longer supported in VASP.5.2.4 and newer versions.
The flag {{TAG|ENCUTFOCK}} is no longer supported in VASP.5.2.4 and newer versions.
Please use {{TAG|PRECFOCK}} instead (see Sec. \ref{incar-precfock}).\index{INCAR!P!PRECFOCK|textit}
Please use {{TAG|PRECFOCK}} instead.
 


The {{TAG|ENCUTFOCK}} tag sets the energy cutoff that determines the FFT grids used by the Hartree-Fock routines.
The only sensible value for {{TAG|ENCUTFOCK}} is {{TAG|ENCUTFOCK}}=0.
The only sensible value for {{TAG|ENCUTFOCK}} is {{TAG|ENCUTFOCK}}=0.
This implies that the smallest possible FFT grid, which just encloses the cutoff sphere
This implies that the smallest possible FFT grid, which just encloses the cutoff sphere
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but causes slight changes in the total energies and  some noise in the calculated forces.
but causes slight changes in the total energies and  some noise in the calculated forces.
The FFT grid used internally in the exact exchange (Hartree-Fock) routines
The FFT grid used internally in the exact exchange (Hartree-Fock) routines
is written to the OUTCAR file. Simply search for lines starting with
is written to the {{TAG|OUTCAR}} file. Simply search for lines starting with


  FFT grid for exact exchange (Hartree Fock)
  FFT grid for exact exchange (Hartree Fock)
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using {{TAG|ENCUTFOCK}}=0, and to make one final total energy calculation
using {{TAG|ENCUTFOCK}}=0, and to make one final total energy calculation
without the flag {{TAG|ENCUTFOCK}}.
without the flag {{TAG|ENCUTFOCK}}.
== Related tags and articles ==
{{TAG|PRECFOCK}},
{{TAG|PREC}},
{{TAG|ENCUT}},
[[list_of_hybrid_functionals|List of hybrid functionals]],
[[Hybrid_functionals:_formalism|Hybrid functionals: formalism]]
{{sc|ENCUTFOCK|Examples|Examples that use this tag}}
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[[Category:INCAR tag]][[Category:Exchange-correlation functionals]][[Category:Hybrid_functionals]]

Latest revision as of 09:14, 18 October 2023

ENCUTFOCK = [real] 

Default: none

Description: The ENCUTFOCK tag sets the energy cutoff that determines the FFT grids used by the Hartree-Fock routines.


The flag ENCUTFOCK is no longer supported in VASP.5.2.4 and newer versions. Please use PRECFOCK instead.


The only sensible value for ENCUTFOCK is ENCUTFOCK=0. This implies that the smallest possible FFT grid, which just encloses the cutoff sphere corresponding to the plane wave cutoff, is used. This accelerates the calculations by roughly a factor two to three, but causes slight changes in the total energies and some noise in the calculated forces. The FFT grid used internally in the exact exchange (Hartree-Fock) routines is written to the OUTCAR file. Simply search for lines starting with

FFT grid for exact exchange (Hartree Fock)


In many cases, a sensible approach is to determine the electronic and ionic groundstate using ENCUTFOCK=0, and to make one final total energy calculation without the flag ENCUTFOCK.

Related tags and articles

PRECFOCK, PREC, ENCUT, List of hybrid functionals, Hybrid functionals: formalism

Examples that use this tag