KSPACING: Difference between revisions
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[[Category:INCAR]][[Category:Electronic minimization]] | [[Category:INCAR tag]][[Category:Electronic minimization]] | ||
Revision as of 14:25, 8 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 [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= \mathrm{max}(1, | \vec{b}_i| / \mathrm{KSPACING} ). }[/math] These values are rounded to the next integer greater than or equal to [math]\displaystyle{ N }[/math]. In this equation, [math]\displaystyle{ \vec{b}_i }[/math] are the reciprocal lattice vectors [math]\displaystyle{ \vec{b}_i \vec{a}_j = 2 \pi \delta_{ij} }[/math]. The generated grid is either centred at the [math]\displaystyle{ \Gamma }[/math] point, i.e., includes the [math]\displaystyle{ \Gamma }[/math] point when (KGAMMA=.TRUE., or is shifted away from the [math]\displaystyle{ \Gamma }[/math] point, as done for Monkhorst-Pack grids when (KGAMMA=.FALSE.. The default is to include the [math]\displaystyle{ \Gamma }[/math] 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, [math]\displaystyle{ N }[/math] is calculated as [math]\displaystyle{ N= \mathrm{max}(1, | \vec{b}_i| / (2 \pi \times \mathrm{KSPACING}) ) }[/math] 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.