KERNEL_TRUNCATION/LTRUNCATE

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KERNEL_TRUNCATION/LTRUNCATE = .True. | .False.
Default: KERNEL_TRUNCATION/LTRUNCATE = .False. 

Description: Truncates the Coulomb kernel to remove electrostatic interactions along non-periodic dimensions.


Setting KERNEL_TRUNCATION/LTRUNCATE = T switches on the Coulomb-kernel-truncation method[1][2][3]. It effectively removes interactions with periodic replicas in non-periodic directions. In other words, the interactions are removed along the surface normal for 2D materials, and along all directions for 0D systems, i.e. for isolated atoms and molecules.

Important: Slabs must be centered in the unit cell.

In the simplest implementation of the Coulomb-kernel-truncation method (KERNEL_TRUNCATION/LCOARSEN = F), the computational cell provided in the POSCAR file is internally padded by an additional vacuum (see KERNEL_TRUNCATION/IPAD). This implies increasing the FFT-grid sizes by a certain factor and thus leads to a significant increase in computational cost.

Tip: Use the KERNEL_TRUNCATION/LCOARSEN = T to avoid the increased FFT-grid sizes.
Mind:
  • KERNEL_TRUNCATION/LTRUNCATE acts as a "super-tag", i.e. unless this tag is switched on further options in KERNEL_TRUNCATION will be ignored.
  • This tag is only available as of VASP.6.5.0.

Detailed information about the setting are documented on respective related tags.

Related tags and articles

KERNEL_TRUNCATION/LCOARSEN, KERNEL_TRUNCATION/IDIMENSIONALITY, KERNEL_TRUNCATION/ISURFACE, KERNEL_TRUNCATION/FACTOR, KERNEL_TRUNCATION/IPAD

References