ENCUT: Difference between revisions

Revision as of 06:59, 20 October 2023

ENCUT = [real]

Default: ENCUT

= largest ENMAX in the POTCAR file

Description: ENCUT specifies the energy cutoff for the plane-wave basis set in eV.

All plane waves with a kinetic energy smaller than $E_{\mathrm{cut}}$ are included in the basis set, i.e.,

| \mathbf{G} + \mathbf{k} | < G_{\mathrm{cut}}

with

E_{\mathrm{cut}} = \frac{\hbar^2}{2m} G^2_{\mathrm{cut}}

With this energy cutoff, the number of plane waves included in the basis set depends on the k-point, leading to a superior behavior. For instance, for energy-volume calculations the total number of plane waves changes fairly smoothly according to the volume, while the criterion $| \mathbf{G} | < G_{\mathrm{cut}}$ (i.e. same number of plane waves for all k-points) would lead to a very rough energy-volume curve and, generally, to a slower energy convergence with respect to the basis set size.

The POTCAR files contain a default ENMAX (and ENMIN). Therefore, it is, in principle, not necessary to specify ENCUT in the INCAR file. For calculations with more than one species, the maximum cutoff ENMAX (or ENMIN) value is used for the calculation (see PREC).

Important:

The convergence of the quantity of interest with respect to the energy cutoff ENCUT should always be checked.
We strongly recommend specifying the energy cutoff ENCUT always manually in the INCAR file to ensure the same accuracy between calculations. Otherwise, the default ENCUT may differ among the different calculations (e.g., for the calculation of the cohesive energy), with the consequence that the total energies, for instance, can not be compared.

@@ Line 1: / Line 1: @@
 {{TAGDEF|ENCUT|[real]}}
-{{DEF|ENCUT|  largest {{TAG|ENMAX}} on the {{FILE|POTCAR}} file | }}
+{{DEF|ENCUT| largest {{TAG|ENMAX}} in the {{FILE|POTCAR}} file | }}
-Description: {{TAG|ENCUT}} specifies the cutoff energy for the planewave basis set in eV.
+Description: {{TAG|ENCUT}} specifies the energy cutoff for the plane-wave basis set in eV.
 ----
 All plane waves with a kinetic energy smaller than <math>E_{\mathrm{cut}}</math> are included in the basis set, i.e.,
-<math> | \mathbf{G} + \mathbf{k} | < G_{\mathrm{cut}} </math> with <math> E_{\mathrm{cut}} = \frac{\hbar^2}{2m} G^2_{\mathrm{cut}} </math>
+::<math> | \mathbf{G} + \mathbf{k} | < G_{\mathrm{cut}} </math> with <math> E_{\mathrm{cut}} = \frac{\hbar^2}{2m} G^2_{\mathrm{cut}} </math>
-The number of plane waves differs for each '''k'''-point, leading to a superior behaviour for, e.g. energy-volume calculations.
+With this energy cutoff, the number of plane waves included in the basis set depends on the '''k'''-point, leading to a superior behavior. For instance, for energy-volume calculations the total number of plane waves changes fairly smoothly according to the volume, while the criterion <math>| \mathbf{G} | < G_{\mathrm{cut}} </math> (i.e. same number of plane waves for all '''k'''-points) would lead to a very rough energy-volume curve and, generally, to a slower energy convergence with respect to the basis set size.
-If the volume is increased the total number of plane waves changes fairly smoothly.
-The criterion <math>| \mathbf{G} | <   G_{\mathrm{cut}} </math> (i.e. same basis set for each '''k'''-point) would lead to a very rough energy-volume curve and, generally, slower energy convergence.
-The {{FILE|POTCAR}} files contain a default {{TAG|ENMAX}} (and {{TAG|ENMIN}}) line, therefore it is in principle not necessary to specify {{TAG|ENCUT}} in the {{FILE|INCAR}} file.
+The {{FILE|POTCAR}} files contain a default {{TAG|ENMAX}} (and {{TAG|ENMIN}}). Therefore, it is, in principle, not necessary to specify {{TAG|ENCUT}} in the {{FILE|INCAR}} file.
-For calculations with more than one species, the maximum cutoff {{TAG|ENMAX}} or {{TAG|ENMIN}} value is used for the calculation (see {{TAG|PREC}}).
+For calculations with more than one species, the maximum cutoff {{TAG|ENMAX}} (or {{TAG|ENMIN}}) value is used for the calculation (see {{TAG|PREC}}).
-For consistency reasons we still recommend to specify the cutoff manually in the {{FILE|INCAR}} file and keep it constant throughout a set of calculations.
+{{NB|important|
+*The convergence of the quantity of interest with respect to the energy cutoff {{TAG|ENCUT}} should always be checked.
+*We strongly recommend specifying the energy cutoff {{TAG|ENCUT}} always manually in the {{FILE|INCAR}} file to ensure the same accuracy between calculations. Otherwise, the default {{TAG|ENCUT}} may differ among the different calculations (e.g., for the calculation of the cohesive energy), with the consequence that the total energies, for instance, can not be compared.}}
-== Related Tags and Sections ==
+== Related tags and articles ==
 {{TAG|ENMAX}},
 {{TAG|ENMIN}},
 {{TAG|ENINI}},
+{{TAG|ENAUG}},
 {{TAG|PREC}},
-{{FILE|POTCAR}},
+{{TAG|NGX}},
-[[Precision|Precision]]
+{{TAG|NGY}},
+{{TAG|NGZ}},
+{{TAG|NGXF}},
+{{TAG|NGYF}},
+{{TAG|NGZF}},
+{{FILE|POTCAR}}
+{{sc|ENCUT|Examples|Examples that use this tag}}
-== Example Calculations using this Tag ==
-{{TAG|Alpha-AlF3}}, {{TAG|Alpha-SiO2}}, {{TAG|cd Si}}, {{TAG|cd Si relaxation}}, {{TAG|Constraining the local magnetic moments}}, {{TAG|Determining the Magnetic Anisotropy}}, {{TAG|Dielectric properties of Si using BSE}}, {{TAG|Dielectric properties of Si using BSE}}, {{TAG|Estimation of J magnetic coupling}}, {{TAG|fcc Ni}}, {{TAG|fcc Ni DOS}}, {{TAG|fcc Si}}, {{TAG|fcc Si bandstructure}}, {{TAG|fcc Si DOS}}, {{TAG|Including the Spin-Orbit Coupling}}, {{TAG|Model BSE calculation on Si}}, {{TAG|Ni 100 surface relaxation}}, {{TAG|NiO GGA+U}}, {{TAG|NiO HSE06}}, {{TAG|NiO LSDA}}, {{TAG|Spin-orbit coupling in a Fe monolayer}}, {{TAG|Spin-orbit coupling in a Ni monolayer}}
-[[Special:Search/ENCUT {{incat|Category:Examples}}]]
-[http://cms.mpi.univie.ac.at/wiki/index.php?title=Special%3ASearch&profile=default&search=ENCUT+%22%5B%5BCategory%3AExamples%5D%5D%22&fulltext=Search Examples]
 ----
-[[The_VASP_Manual|Contents]]
-[[Category:INCAR]]
+[[Category:INCAR tag]][[Category:Electronic minimization]]