KERNEL TRUNCATION/LCOARSEN - Revision history

Huebsch at 10:58, 17 March 2026

2026-03-17T10:58:56Z

← Older revision		Revision as of 10:58, 17 March 2026
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	{{TAGDEF\|KERNEL_TRUNCATION/LCOARSEN\| .True. {{!}} .False.\|.False.}}		{{TAGDEF\|KERNEL_TRUNCATION/LCOARSEN\| .True. {{!}} .False.\|.False.}}
	{{DISPLAYTITLE:KERNEL_TRUNCATION/LCOARSEN}}		{{DISPLAYTITLE:KERNEL_TRUNCATION/LCOARSEN}}

	Description: Coarsen the charge density before padding to speed up the computation of the local potential in the Coulomb-kernel-truncation method.		Description: Coarsen the charge density before padding to speed up the computation of the local potential in the Coulomb-kernel-truncation method.
	----		----

Huebsch at 10:58, 17 March 2026

2026-03-17T10:58:49Z

← Older revision		Revision as of 10:58, 17 March 2026
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	{{TAGDEF\|KERNEL_TRUNCATION/LCOARSEN\| .True. {{!}} .False.\|.False.}}		{{TAGDEF\|KERNEL_TRUNCATION/LCOARSEN\| .True. {{!}} .False.\|.False.}}
			{{DISPLAYTITLE:KERNEL_TRUNCATION/LCOARSEN}}

	Description: Coarsen the charge density before padding to speed up the computation of the local potential in the Coulomb-kernel-truncation method.		Description: Coarsen the charge density before padding to speed up the computation of the local potential in the Coulomb-kernel-truncation method.

Huebsch at 10:49, 17 March 2026

2026-03-17T10:49:37Z

← Older revision		Revision as of 10:49, 17 March 2026
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	* The full electrostatic potential is first computed under standard 3D periodic boundary conditions.		* The full electrostatic potential is first computed under standard 3D periodic boundary conditions.
	* A coarse representation of the charge density ~~with <math>1/3</math> of the~~ [[Energy cutoff and FFT meshes\|FFT-grid ~~size~~]] is constructed by retaining only the long-wavelength (low-\|G\|) components responsible for long-range interactions.		* A coarse representation of the charge density on a reduced [[Energy cutoff and FFT meshes\|FFT-grid]] which is constructed by retaining only the long-wavelength (low-\|G\|) components responsible for long-range interactions.
	* The truncated Coulomb kernel is applied only to this coarse density using a padded grid.		* The truncated Coulomb kernel is applied only to this coarse density using a padded grid (see {{TAG\|KERNEL_TRUNCATION/IPAD}}).
	* The final potential is obtained by subtracting the long-range periodic contribution and replacing it with the correctly truncated one.		* The final potential is obtained by subtracting the long-range periodic contribution and replacing it with the correctly truncated one.

Huebsch at 10:43, 17 March 2026

2026-03-17T10:43:14Z

← Older revision		Revision as of 10:43, 17 March 2026
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	{{TAGDEF\|KERNEL_TRUNCATION/LCOARSEN\| .True. {{!}} .False.\|.~~True~~.}}		{{TAGDEF\|KERNEL_TRUNCATION/LCOARSEN\| .True. {{!}} .False.\|.False.}}

	Description: Coarsen the charge density before padding to speed up the computation of the local potential in the Coulomb-kernel-truncation method.		Description: Coarsen the charge density before padding to speed up the computation of the local potential in the Coulomb-kernel-truncation method.

Huebsch at 10:22, 17 March 2026

2026-03-17T10:22:33Z

← Older revision		Revision as of 10:22, 17 March 2026
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	{{TAGDEF\|KERNEL_TRUNCATION/LCOARSEN\| .True. {{!}} .False.\|.True.}}		{{TAGDEF\|KERNEL_TRUNCATION/LCOARSEN\| .True. {{!}} .False.\|.True.}}

	Description: ~~{{TAG\|KERNEL_TRUNCATION/LCOARSEN}} speeds~~ up computation of the local potential in the kernel truncation method ~~by coarsening the charge density before padding it~~		Description: Coarsen the charge density before padding to speed up the computation of the local potential in the Coulomb-kernel-truncation method.
	----		----
			The Coulomb-kernel-truncation method ({{TAG\|KERNEL_TRUNCATION/LTRUNCATE}}) modifies the electrostatic potential to remove spurious interactions between periodic images in systems with reduced dimensionality (e.g. molecules or surfaces).
			{{TAG\|KERNEL_TRUNCATION/LCOARSEN\|T}} avoids significantly increasing [[Energy cutoff and FFT meshes\|FFT-grid sizes]] by using a ''coarsen-before-padding'' approach:

	~~Kernel truncation methods pad~~ the ~~computational cell~~ with ~~vacuum~~.		* The full electrostatic potential is first computed under standard 3D periodic boundary conditions.
	~~This padded cell~~ is ~~expensive to compute due~~ to ~~FFTs being performed on~~ a ~~larger~~ grid.		* A coarse representation of the charge density with <math>1/3</math> of the [[Energy cutoff and FFT meshes\|FFT-grid size]] is constructed by retaining only the long-wavelength (low-\|G\|) components responsible for long-range interactions.
	The ~~{{TAG\|KERNEL_TRUNCATION/LCOARSEN}} method selectively replaces~~ the long range ~~potential~~ with the truncated ~~potential instead of computing the entire potential on a padded grid~~.		* The truncated Coulomb kernel is applied only to this coarse density using a padded grid.
	This ~~selective replacement~~ of the ~~potential bypasses the need for padding~~, ~~speeding up~~ the ~~computation~~ of ~~the kernel truncation methods~~.		* The final potential is obtained by subtracting the long-range periodic contribution and replacing it with the correctly truncated one.
	{{NB\|mind\|IF {{TAG\|KERNEL_TRUNCATION/LTRUNCATE}} ~~is switched off~~, all other KERNEL_TRUNCATION tags~~, i.e. {{TAG\|KERNEL_TRUNCATION/IDIMENSIONALITY}},~~ {{TAG\|KERNEL_TRUNCATION/LCOARSEN}}~~, and {{TAG\|KERNEL_TRUNCATION/ISURFACE}} will be~~ ignored.}}
			This procedure exploits the fact that [[electrostatics \|long-range electrostatics]] depends only on low-frequency components of the charge density, allowing the expensive padded FFTs to be performed on a much smaller grid with minimal loss of accuracy.
			{{NB\|mind\|If {{TAG\|KERNEL_TRUNCATION/LTRUNCATE\|F}}, all other KERNEL_TRUNCATION tags including {{TAG\|KERNEL_TRUNCATION/LCOARSEN}} are ignored.}}

	== Related tags and articles ==		== Related tags and articles ==
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	{{TAG\|KERNEL_TRUNCATION/FACTOR}}		{{TAG\|KERNEL_TRUNCATION/FACTOR}}

	[[Category:INCAR tag]][[Category:Electrostatics]]		[[Category:INCAR tag]][[Category:Electrostatics]][[Category:2D materials]]

Miranda.henrique at 08:19, 14 October 2025

2025-10-14T08:19:58Z

← Older revision		Revision as of 08:19, 14 October 2025
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	{{TAG\|KERNEL_TRUNCATION/LTRUNCATE}},		{{TAG\|KERNEL_TRUNCATION/LTRUNCATE}},
	{{TAG\|KERNEL_TRUNCATION/IDIMENSIONALITY}},		{{TAG\|KERNEL_TRUNCATION/IDIMENSIONALITY}},
	{{TAG\|KERNEL_TRUNCATION/ISURFACE}}		{{TAG\|KERNEL_TRUNCATION/ISURFACE}},
			{{TAG\|KERNEL_TRUNCATION/IPAD}},
			{{TAG\|KERNEL_TRUNCATION/FACTOR}}

	[[Category:INCAR tag]][[Category:Electrostatics]]		[[Category:INCAR tag]][[Category:Electrostatics]]

Schlipf at 07:25, 16 June 2025

2025-06-16T07:25:06Z

← Older revision		Revision as of 07:25, 16 June 2025
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	{{TAG\|KERNEL_TRUNCATION/ISURFACE}}		{{TAG\|KERNEL_TRUNCATION/ISURFACE}}

	[[Category:INCAR tag]]		[[Category:INCAR tag]][[Category:Electrostatics]]

Csheldon at 08:51, 19 December 2024

2024-12-19T08:51:18Z

← Older revision		Revision as of 08:51, 19 December 2024
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	The {{TAG\|KERNEL_TRUNCATION/LCOARSEN}} method selectively replaces the long range potential with the truncated potential instead of computing the entire potential on a padded grid.		The {{TAG\|KERNEL_TRUNCATION/LCOARSEN}} method selectively replaces the long range potential with the truncated potential instead of computing the entire potential on a padded grid.
	This selective replacement of the potential bypasses the need for padding, speeding up the computation of the kernel truncation methods.		This selective replacement of the potential bypasses the need for padding, speeding up the computation of the kernel truncation methods.
			{{NB\|mind\|IF {{TAG\|KERNEL_TRUNCATION/LTRUNCATE}} is switched off, all other KERNEL_TRUNCATION tags, i.e. {{TAG\|KERNEL_TRUNCATION/IDIMENSIONALITY}}, {{TAG\|KERNEL_TRUNCATION/LCOARSEN}}, and {{TAG\|KERNEL_TRUNCATION/ISURFACE}} will be ignored.}}

	== Related tags and articles ==		== Related tags and articles ==

Svijay at 10:48, 18 December 2024

2024-12-18T10:48:23Z

← Older revision		Revision as of 10:48, 18 December 2024
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	{{TAG\|KERNEL_TRUNCATION/IDIMENSIONALITY}},		{{TAG\|KERNEL_TRUNCATION/IDIMENSIONALITY}},
	{{TAG\|KERNEL_TRUNCATION/ISURFACE}}		{{TAG\|KERNEL_TRUNCATION/ISURFACE}}

			[[Category:INCAR tag]]

Svijay: Svijay moved page Construction:KERNEL TRUNCATION/LCOARSEN to KERNEL TRUNCATION/LCOARSEN

2024-12-18T09:35:57Z

Svijay moved page Construction:KERNEL TRUNCATION/LCOARSEN to KERNEL TRUNCATION/LCOARSEN

← Older revision	Revision as of 09:35, 18 December 2024
(No difference)

← Older revision		Revision as of 08:19, 14 October 2025
Line 13:		Line 13:
	{{TAG\|KERNEL_TRUNCATION/LTRUNCATE}},		{{TAG\|KERNEL_TRUNCATION/LTRUNCATE}},
	{{TAG\|KERNEL_TRUNCATION/IDIMENSIONALITY}},		{{TAG\|KERNEL_TRUNCATION/IDIMENSIONALITY}},
	{{TAG\|KERNEL_TRUNCATION/ISURFACE}}		{{TAG\|KERNEL_TRUNCATION/ISURFACE}},
			{{TAG\|KERNEL_TRUNCATION/IPAD}},
			{{TAG\|KERNEL_TRUNCATION/FACTOR}}

	[[Category:INCAR tag]][[Category:Electrostatics]]		[[Category:INCAR tag]][[Category:Electrostatics]]