KSPACING OPT: Difference between revisions
(Created new KSPACING_OPT wiki page with information about k-point mesh generation for the KPOINTS_OPT driver) |
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{{TAGDEF|KSPACING_OPT|[real]|0.5}} | {{TAGDEF|KSPACING_OPT|[real]|0.5}} | ||
Description: The tag {{TAG|KSPACING_OPT}} determines the number of k points for the {{TAG|KPOINTS_OPT}} driver if the {{FILE|KPOINTS_OPT}} file is not present. | Description: The tag {{TAG|KSPACING_OPT}} determines the number of k points for the {{TAG|KPOINTS_OPT}} driver if the {{FILE|KPOINTS_OPT}} file is not present. | ||
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with <math>\mathrm{ceiling}( x )</math> being the ceiling function which returns the least integer that is equal or larger than <math>x</math>. In this equation, <math> \mathbf{b}_i </math> are the reciprocal lattice vectors <math> \mathbf{b}_i \mathbf{a}_j = \delta_{ij} </math>. | with <math>\mathrm{ceiling}( x )</math> being the ceiling function which returns the least integer that is equal or larger than <math>x</math>. In this equation, <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}}=True (default), i.e., includes the <math>\Gamma</math> point. For {{TAG|KGAMMA}}=False, the grid is shifted away from the <math>\Gamma</math> point as done for Monkhorst-Pack grids. | The generated grid is centered at the <math>\Gamma</math> point if {{TAG|KGAMMA}}=True (default), i.e., includes the <math>\Gamma</math> point. For {{TAG|KGAMMA}}=False, the grid is shifted away from the <math>\Gamma</math> point as done for Monkhorst-Pack grids. | ||
{{NB|tip|This feature is only available since VASP 6.6.0.}} | |||
== Related tags and articles == | == Related tags and articles == | ||
Revision as of 10:57, 20 March 2026
KSPACING_OPT = [real]
Default: KSPACING_OPT = 0.5
Description: The tag KSPACING_OPT determines the number of k points 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] with [math]\displaystyle{ \mathrm{ceiling}( x ) }[/math] being the ceiling function which returns the least integer that is equal or larger than [math]\displaystyle{ x }[/math]. In this equation, [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=True (default), i.e., includes the [math]\displaystyle{ \Gamma }[/math] point. For KGAMMA=False, the grid is shifted away from the [math]\displaystyle{ \Gamma }[/math] point as done for Monkhorst-Pack grids.
| Tip: This feature is only available since VASP 6.6.0. |
Related tags and articles
KSPACING, KGAMMA, KPOINTS_OPT, KPOINTS