ENCUTFOCK: Difference between revisions
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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. | Please use {{TAG|PRECFOCK}} instead. | ||
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 | ||
Revision as of 19:48, 15 January 2017
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 Sections
PRECFOCK, PREC, ENCUT, hybrid functionals, settings for specific hybrid functionals