ENCUT: Difference between revisions

Latest 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_{\mathrm {cut} }^{2}

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}} from the {{FILE|POTCAR}}-file | }}
+{{DEF|ENCUT| largest {{TAG|ENMAX}} in the {{FILE|POTCAR}} file | }}
-Description: {{TAG|EMAX}} specifies the  Cut-off energy for plane wave
+Description: {{TAG|ENCUT}} specifies the energy cutoff for the plane-wave basis set in eV.
-basis set in eV.
 ----
-All plane-waves with a kinetic energy smaller than
+All plane waves with a kinetic energy smaller than <math>E_{\mathrm{cut}}</math> are included in the basis set, i.e.,
-<math>E_{\mathrm{cut}}</math>
-are included in the basis set: i.e.
-<math> | \mathbf{G} + \mathbf{k} | </math> with <math> E_{\mathrm{cut}} =
+::<math> | \mathbf{G} + \mathbf{k} | < G_{\mathrm{cut}} </math> with <math> E_{\mathrm{cut}} = \frac{\hbar^2}{2m} G^2_{\mathrm{cut}} </math>
-\frac{\hbar^2}{2m} G^2_{\mathrm{cut}} </math>
-The number of plane waves differs for each k-point, leading to a superior
+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.
-beahviour for e.g. energy-volume calculations. 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
-<math>\mathbf{k}</math>-point)
-would lead to a very rough energy-volume curve and, generally, slower energy convergence.
-Starting from version VASP 3.2 the {{FILE|POTCAR}} files contains a default
+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.
-{{TAG|ENMAX}} (and {{TAG|ENMIN}}) line,
+For calculations with more than one species, the maximum cutoff {{TAG|ENMAX}} (or {{TAG|ENMIN}}) value is used for the calculation (see {{TAG|PREC}}).
-therefore it is in principle not necessary to specify {{TAG|ENCUT}} in
+{{NB|important|
-the {{FILE|INCAR}} file. For calculations
+*The convergence of the quantity of interest with respect to the energy cutoff {{TAG|ENCUT}} should always be checked.
-with more than one species, the maximum cutoff {{TAG|ENMAX}} or {{TAG|ENMIN}}
+*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.}}
-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 in constant throughout a set of calculations.
-== Related Tags and Sections ==
+== Related tags and articles ==
 {{TAG|ENMAX}},
 {{TAG|ENMIN}},
+{{TAG|ENINI}},
+{{TAG|ENAUG}},
+{{TAG|PREC}},
+{{TAG|NGX}},
+{{TAG|NGY}},
+{{TAG|NGZ}},
+{{TAG|NGXF}},
+{{TAG|NGYF}},
+{{TAG|NGZF}},
 {{FILE|POTCAR}}
-[[Precision|Precision]]
+{{sc|ENCUT|Examples|Examples that use this tag}}
 ----
-[[The_VASP_Manual|Contents]]
-[[Category:INCAR]]
+[[Category:INCAR tag]][[Category:Electronic minimization]]