ENCUTFOCK

ENCUTFOCK = [real] 

Default: none

The flag 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 ENCUTFOCK tag sets the energy cutoff that determines the FFT grids used by the Hartree-Fock routines. 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 \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 ENCUTFOCK=0, and to make one final total energy calculation without the flag ENCUTFOCK.