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# ENCUTFOCK

**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