ENCUTFOCK: Difference between revisions
(Created page with "{{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. \re...") |
No edit summary |
||
| Line 6: | Line 6: | ||
Please use {\tt PRECFOCK} instead (see Sec. \ref{incar-precfock}).\index{INCAR!P!PRECFOCK|textit} | Please use {\tt PRECFOCK} instead (see Sec. \ref{incar-precfock}).\index{INCAR!P!PRECFOCK|textit} | ||
The { | The {{TAG|ENCUTFOCK}} tag sets the energy cutoff that determines the FFT grids used by the Hartree-Fock routines. | ||
The only sensible value for { | 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 | ||
corresponding to the plane wave cutoff, is used. | corresponding to the plane wave cutoff, is used. | ||
Revision as of 12:22, 14 January 2017
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 {\tt ENCUTFOCK}=0, and to make one final total energy calculation without the flag {\tt ENCUTFOCK}.