View source for ENCUTFOCK

{{TAGDEF|ENCUTFOCK|[real]}}

Default: none

The flag {{TAG|ENCUTFOCK}} is no longer supported in VASP.5.2.4 and newer versions.
Please use {\tt PRECFOCK} instead (see Sec. \ref{incar-precfock}).\index{INCAR!P!PRECFOCK|textit}

The {\tt ENCUTFOCK} tag sets the energy cutoff that determines the FFT grids used by the Hartree-Fock routines.
The only sensible value for {\tt ENCUTFOCK} is {\tt 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
\begin{verbatim}
 FFT grid for exact exchange (Hartree Fock)
\end{verbatim}

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