KERNEL TRUNCATION/IPAD

KERNEL_TRUNCATION/IPAD = integer 

Default: KERNEL_TRUNCATION/IPAD	= 3	if KERNEL_TRUNCATION/IDIMENSIONALITY = 0
	= 2	if KERNEL_TRUNCATION/IDIMENSIONALITY = 2

Description: KERNEL_TRUNCATION/IPAD controls the padding strategy used for the Coulomb kernel truncation in reciprocal space. Padding defines how much additional empty space is introduced around the charge density before applying truncation. This affects both the accuracy of the truncated Coulomb potential and the computational cost.

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Setting KERNEL_TRUNCATION/IPAD allows fine control over how much zero-padding is applied along each reciprocal-space direction. Padding ensures that the truncated Coulomb kernel does not artificially interact with its periodic replicas in non-periodic directions.

Typically, increasing KERNEL_TRUNCATION/IPAD improves accuracy at the expense of computational cost.

Mind: KERNEL_TRUNCATION/LTRUNCATE must be set to .TRUE. for KERNEL_TRUNCATION/IPAD to have any effect.

Default settings

The value of KERNEL_TRUNCATION/IPAD depends on the system dimensionality:

System type	Typical KERNEL_TRUNCATION/IDIMENSIONALITY	Default KERNEL_TRUNCATION/IPAD
Molecules (0D)	0	3
Layer materials (2D)	2	2

Example:

KERNEL_TRUNCATION {
     LTRUNCATE      = T
     IDIMENSIONALITY = 2
     IPAD            = 1
}

This corresponds to truncation along the surface normal (z-direction) for a 2D material with one layer of padding.

Related tags and articles

KERNEL_TRUNCATION/LTRUNCATE, KERNEL_TRUNCATION/IDIMENSIONALITY, KERNEL_TRUNCATION/LCOARSEN, KERNEL_TRUNCATION/ISURFACE