KERNEL TRUNCATION/FACTOR: Difference between revisions

Latest revision as of 11:25, 17 March 2026

Default: KERNEL_TRUNCATION/FACTOR	= $\sqrt{3}$	if `KERNEL_TRUNCATION/IDIMENSIONALITY = 0`
	= 1	if `KERNEL_TRUNCATION/IDIMENSIONALITY = 2`

Description: Determines the spatial extent of the truncated Coulomb interaction relative to the computational cell dimension along the truncation direction.

KERNEL_TRUNCATION/FACTOR defines the cutoff distance of the Coulomb-kernel-truncation boundary. It is expressed as a fraction of the simulation-cell length along the truncated axis (e.g., the surface normal for 2D systems ISURFACE).

Mind:

IfKERNEL_TRUNCATION/LTRUNCATE = F, KERNEL_TRUNCATION/FACTOR is ignored.
Available as of VASP.6.5.0.

@@ Line 1: / Line 1: @@
 {{TAGDEF|KERNEL_TRUNCATION/FACTOR| real}}
-{{DEF|KERNEL_TRUNCATION/FACTOR|$\sqrt{3}$|if {{TAGO|KERNEL_TRUNCATION/IDIMENSIONALITY|0}}|1|if {{TAGO|KERNEL_TRUNCATION/IDIMENSIONALITY|2}}}}
+{{DEF|KERNEL_TRUNCATION/FACTOR|$\sqrt{3}$|if {{TAG|KERNEL_TRUNCATION/IDIMENSIONALITY|0}}|1|if {{TAG|KERNEL_TRUNCATION/IDIMENSIONALITY|2}}}}
+{{DISPLAYTITLE:KERNEL_TRUNCATION/FACTOR}}
 '''Description:'''
-{{TAG|KERNEL_TRUNCATION/FACTOR}} determines the spatial extent of the truncated Coulomb interaction relative to the full cell dimension along the truncation direction{{cite|vijay:arxiv:2024}}.
+Determines the spatial extent of the truncated Coulomb interaction relative to the computational cell dimension along the truncation direction.
 ----
-This tag defines the cutoff distance of the Coulomb kernel truncation boundary. It is expressed as a fraction of the simulation cell length along the truncated axis (e.g., the surface normal for 2D systems).
+{{TAG|KERNEL_TRUNCATION/FACTOR}} defines the cutoff distance of the Coulomb-kernel-truncation boundary. It is expressed as a fraction of the simulation-cell length along the truncated axis (e.g., the surface normal for 2D systems {{TAG|ISURFACE}}).
-{{NB|mind|{{TAG|KERNEL_TRUNCATION/LTRUNCATE}} must be set to <code>.TRUE.</code> for {{TAG|KERNEL_TRUNCATION/FACTOR}} to take effect.}}
+{{NB|mind|
+*If{{TAG|KERNEL_TRUNCATION/LTRUNCATE|F}}, {{TAG|KERNEL_TRUNCATION/FACTOR}} is ignored.
-== Example ==
+*Available as of VASP.6.5.0.}}
-<pre>
-KERNEL_TRUNCATION {
-     LTRUNCATE       = T
-     IDIMENSIONALITY = 2
-     ISURFACE        = 3
-     IPAD            = 2
-     FACTOR          = 1
-}
-</pre>
-In this case an additional empty cell is added along the z direciton as padding. The coulomb interaction is truncated beyond a z length. This ensures maximum usage of the simulation box.
-<pre>
-KERNEL_TRUNCATION {
-     LTRUNCATE       = T
-     IDIMENSIONALITY = 2
-     ISURFACE        = 3
-     IPAD            = 1
-     FACTOR          = 0.5
-}
-</pre>
-This setup corresponds to truncating the Coulomb interaction along the surface normal (z-direction) for a 2D material, using no vacuum padding and a truncation length of z/2. In this case, half of the simulation box is effectively unused, but the algorithm remains simpler. This configuration can be useful for debugging purposes.
 == Related tags and articles ==
@@ Line 41: / Line 18: @@
 {{TAG|KERNEL_TRUNCATION/IPAD}},
 {{TAG|KERNEL_TRUNCATION/ISURFACE}}
-== References ==
 [[Category:INCAR tag]]
 [[Category:Electrostatics]]