ENCUT: Difference between revisions

Revision as of 17:26, 11 September 2012

ENCUT = [real]

Default: ENCUT

= largest ENMAX on the POTCAR file

Description: ENCUT specifies the cutoff energy for the planewave 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 $E_{\mathrm {cut} }={\frac {\hbar ^{2}}{2m}}G_{\mathrm {cut} }^{2}$

The number of plane waves differs for each k-point, leading to a superior behaviour for, e.g. energy-volume calculations. If the volume is increased the total number of plane waves changes fairly smoothly. The criterion $|\mathbf {G} |<G_{\mathrm {cut} }$ (i.e. same basis set for each k-point) would lead to a very rough energy-volume curve and, generally, slower energy convergence.

The POTCAR files contains a default ENMAX (and ENMIN) line, 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). For consistency reasons we still recommend to specify the cutoff manually in the INCAR file and keep in constant throughout a set of calculations.

Related Tags and Sections

ENMAX, ENMIN, PREC, POTCAR, Precision

Contents

@@ Line 1: / Line 1: @@
 {{TAGDEF|ENCUT|[real]}}
-{{DEF|ENCUT|  largest {{TAG|ENMAX}} on the {{FILE|POTCAR}}-file | }}
+{{DEF|ENCUT|  largest {{TAG|ENMAX}} on the {{FILE|POTCAR}} file | }}
-Description: {{TAG|ENCUT}} specifies the cut-off energy for the planewave basis set in eV.
+Description: {{TAG|ENCUT}} specifies the cutoff energy for the planewave 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} | < G_{\mathrm{cut}} </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
+The number of plane waves differs for each '''k'''-point, leading to a superior behaviour for, e.g. energy-volume calculations.
-beahviour for e.g. energy-volume calculations. If the volume is increased the total number
+If the volume is increased the total number of plane waves changes fairly smoothly.
-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 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 contains a default {{TAG|ENMAX}} (and {{TAG|ENMIN}}) line, 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
+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.
-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 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 ==