KSPACING OPT: Difference between revisions
(Created new KSPACING_OPT wiki page with information about k-point mesh generation for the KPOINTS_OPT driver) |
|||
| (2 intermediate revisions by 2 users not shown) | |||
| Line 1: | Line 1: | ||
{{TAGDEF|KSPACING_OPT|[real]|0.5}} | {{TAGDEF|KSPACING_OPT|[real]|0.5}} | ||
{{DISPLAYTITLE:KSPACING_OPT}} | |||
{{ | Description: Spacing between '''k''' points in the automatically generated mesh for the {{TAG|KPOINTS_OPT}} driver if the {{FILE|KPOINTS_OPT}} file is not present. | ||
Description: | |||
---- | ---- | ||
{{TAG|KSPACING_OPT}} is used to define the k-point mesh of the {{TAG|KPOINTS_OPT}} driver, where the wave functions are computed non-self-consistently. This is useful to obtain the density of states on a mesh finer than the one used in the SCF run. | {{TAG|KSPACING_OPT}} is used to define the '''k'''-point mesh of the {{TAG|KPOINTS_OPT}} driver, where the wave functions are computed non-self-consistently. This is useful to obtain the density of states on a mesh finer than the one used in the SCF run. | ||
{{TAG|KSPACING_OPT}} 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. | {{TAG|KSPACING_OPT}} 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. | ||
The number of k points in the direction of the first, second and third reciprocal lattice vector is determined by <math> N_i= \mathrm{max}(1, \mathrm{ceiling}( | \mathbf{b}_i| 2\pi / \mathrm{KSPACING\_OPT} ))</math> | The number of '''k''' points in the direction of the first, second and third reciprocal lattice | ||
vector is determined by <math> N_i= \mathrm{max}(1, \mathrm{ceiling}( | \mathbf{b}_i| 2\pi / \mathrm{KSPACING\_OPT} ))</math>, | |||
The generated grid is centered at the <math>\Gamma</math> point if {{TAG|KGAMMA}} | where <math>\mathrm{ceiling}( x )</math> returns the least integer that is equal or larger than <math>x</math>. Here, <math> \mathbf{b}_i </math> are the reciprocal lattice vectors <math> \mathbf{b}_i \mathbf{a}_j = \delta_{ij} </math>. | ||
The generated grid is centered at the <math>\Gamma</math> point if {{TAG|KGAMMA|T}} (default), i.e., includes the <math>\Gamma</math> point. For {{TAG|KGAMMA|F}}, the grid is shifted away from the <math>\Gamma</math> point as done for Monkhorst-Pack grids. | |||
{{Available|6.6.0}} | |||
== Related tags and articles == | == Related tags and articles == | ||
{{TAG|KSPACING}}, {{TAG|KGAMMA}}, {{TAG| | Tags: {{TAG|KSPACING}}, {{TAG|KGAMMA}}, {{TAG|LKPOINTS_OPT}} | ||
Files: {{FILE|KPOINTS}}, {{FILE|KPOINTS_OPT}} | |||
{{sc|KSPACING_OPT| | {{sc|KSPACING_OPT|HowTo|Workflows that use this tag}} | ||
[[Category:INCAR tag]][[Category:Crystal momentum]] | [[Category:INCAR tag]][[Category:Crystal momentum]] | ||
Latest revision as of 15:34, 20 March 2026
KSPACING_OPT = [real]
Default: KSPACING_OPT = 0.5
Description: Spacing between k points in the automatically generated mesh for the KPOINTS_OPT driver if the KPOINTS_OPT file is not present.
KSPACING_OPT is used to define the k-point mesh of the KPOINTS_OPT driver, where the wave functions are computed non-self-consistently. This is useful to obtain the density of states on a mesh finer than the one used in the SCF run.
KSPACING_OPT is the smallest allowed spacing between k points in units of [math]\displaystyle{ \AA^{-1} }[/math]. 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 [math]\displaystyle{ N_i= \mathrm{max}(1, \mathrm{ceiling}( | \mathbf{b}_i| 2\pi / \mathrm{KSPACING\_OPT} )) }[/math],
where [math]\displaystyle{ \mathrm{ceiling}( x ) }[/math] returns the least integer that is equal or larger than [math]\displaystyle{ x }[/math]. Here, [math]\displaystyle{ \mathbf{b}_i }[/math] are the reciprocal lattice vectors [math]\displaystyle{ \mathbf{b}_i \mathbf{a}_j = \delta_{ij} }[/math].
The generated grid is centered at the [math]\displaystyle{ \Gamma }[/math] point if KGAMMA = T (default), i.e., includes the [math]\displaystyle{ \Gamma }[/math] point. For KGAMMA = F, the grid is shifted away from the [math]\displaystyle{ \Gamma }[/math] point as done for Monkhorst-Pack grids.
| Mind: Available as of VASP 6.6.0 |
Related tags and articles
Tags: KSPACING, KGAMMA, LKPOINTS_OPT
Files: KPOINTS, KPOINTS_OPT