KSPACING: Difference between revisions
No edit summary |
No edit summary |
||
| Line 1: | Line 1: | ||
{{TAGDEF|KSPACING|[real]|0.5}} | {{TAGDEF|KSPACING|[real]|0.5}} | ||
Description: The tag {{TAG|KSPACING}} determines the number of k | Description: The tag {{TAG|KSPACING}} determines the number of k points if the {{TAG|KPOINTS}} file | ||
is not present. | is not present. | ||
---- | ---- | ||
{{TAG|KSPACING}} is the smallest allowed spacing between k points in units of | {{TAG|KSPACING}} is the smallest allowed spacing between k points in units of <math>\AA^{-1}</math>. The number of k points increases when the spacing is decreased. | ||
<math>\AA^{-1}</math>. The number of k | The number of k points in the direction of the first, second and third reciprocal lattice vector is determined by <math> N= \mathrm{max}(1, | \vec{b}_i| / \mathrm{KSPACING} ). </math> | ||
The number of k | These values are rounded to the next integer greater than or equal to <math> N </math>. In this equation, <math> \vec{b}_i </math> are the reciprocal lattice vectors <math> \vec{b}_i \vec{a}_j = 2 \pi \delta_{ij} </math>. | ||
reciprocal lattice vector is determined by <math> N= \mathrm{max}(1, | \vec{b}_i| / \mathrm{KSPACING} ). </math> | The generated grid is either centred at the <math>\Gamma</math> point, i.e., includes the <math>\Gamma</math> point when ({{TAG|KGAMMA}}=.TRUE., or is shifted away from the <math>\Gamma</math> point, as done for Monkhorst-Pack grids when ({{TAG|KGAMMA}}=.FALSE.. The default is to include the <math>\Gamma</math> point. | ||
These values are rounded to the next integer greater than or equal to <math> N </math>. In this equation | {{NB|warning|This implementation is not entirely consistent with the automatic k-point generation (Mode{{=}}A) used in the {{FILE|KPOINTS}} file.}} | ||
<math> \vec{b}_i </math> | If the k points are generated using the automatic mode in the {{FILE|KPOINTS}} file, <math> N</math> is calculated as | ||
are the reciprocal lattice vectors <math> \vec{b}_i \vec{a}_j = 2 \pi \delta_{ij} </math>. | |||
The generated grid is either centred at the <math>\Gamma</math> point | |||
from the <math>\Gamma</math> point, as | |||
The default is to include the <math>\Gamma</math> point. | |||
(Mode=A) used in the KPOINTS file. If the k | |||
in the KPOINTS file, <math> N</math> is calculated as | |||
<math> N= \mathrm{max}(1, | \vec{b}_i| / (2 \pi \times \mathrm{KSPACING}) ) </math> | <math> N= \mathrm{max}(1, | \vec{b}_i| / (2 \pi \times \mathrm{KSPACING}) ) </math> | ||
and rounding is to the nearest integer. We recommend | and rounding is to the nearest integer. We recommend using the {{TAG|KSPACING}} tag in the {{FILE|INCAR}} file | ||
and | and avoiding the automatic mode via the {{FILE|KPOINTS}} file. | ||
== Related | == Related tags and articles == | ||
{{TAG|KGAMMA}} | {{TAG|KGAMMA}}, {{FILE|KPOINTS}} | ||
{{sc|KSPACING|Examples|Examples that use this tag}} | {{sc|KSPACING|Examples|Examples that use this tag}} | ||
| Line 31: | Line 23: | ||
[[The_VASP_Manual|Contents]] | [[The_VASP_Manual|Contents]] | ||
[[Category:INCAR]][[Category:Electronic | [[Category:INCAR]][[Category:Electronic minimization]] | ||
Revision as of 12:53, 6 April 2022
KSPACING = [real]
Default: KSPACING = 0.5
Description: The tag KSPACING determines the number of k points if the KPOINTS file is not present.
KSPACING is the smallest allowed spacing between k points in units of . The number of k points increases when the spacing is decreased. The number of k points in the direction of the first, second and third reciprocal lattice vector is determined by These values are rounded to the next integer greater than or equal to . In this equation, are the reciprocal lattice vectors . The generated grid is either centred at the point, i.e., includes the point when (KGAMMA=.TRUE., or is shifted away from the point, as done for Monkhorst-Pack grids when (KGAMMA=.FALSE.. The default is to include the point.
| Warning: This implementation is not entirely consistent with the automatic k-point generation (Mode=A) used in the KPOINTS file. |
If the k points are generated using the automatic mode in the KPOINTS file, is calculated as and rounding is to the nearest integer. We recommend using the KSPACING tag in the INCAR file and avoiding the automatic mode via the KPOINTS file.