KERNEL TRUNCATION/IDIMENSIONALITY

KERNEL_TRUNCATION/IDIMENSIONALITY_CUTOFF = 0 | 2 | 3
Default: KERNEL_TRUNCATION/IDIMENSIONALITY_CUTOFF = 3 

Description: KERNEL_TRUNCATION/IDIMENSIONALITY_CUTOFF specifies the boundary condition used to compute the hartree and ionic potential

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If KERNEL_TRUNCATION/LTRUNCATE_KERNEL = T, KERNEL_TRUNCATION/IDIMENSIONALITY_CUTOFF determines the boundary condition that is used to compute the local potential. The default value of 3 implies that the system is periodic in all dimensions, i.e. there is no influence of kernel truncation on the resulting energies and forces. Setting KERNEL_TRUNCATION/IDIMENSIONALITY_CUTOFF to either 0 or 2 uses the 0D and 2D truncated kernel respectively [cite]. These kernels create 0D (i.e. no periodic interactions, as is the case of molecules) and 2D (i.e. periodic interactions only in two dimensions, as in the case for surfaces).

KERNEL_TRUNCATION/IDIMENSIONALITY_CUTOFF = 0

Consider using the option when computing energies and forces of atoms and molecules. Recommended INCAR tags to be used with option are

 KERNEL_TRUNCATION {
       LTRUNCATE_COULOMB_KERNEL = T
       IDIMENIONALITY_CUTOFF    = 0
       LCOARSEN_BEFORE_PAD      = T
 }

KERNEL_TRUNCATION/IDIMENSIONALITY_CUTOFF = 2

Use this option when computing the energies and forces of 2D and quasi-2D systems, such as 2D materials and surfaces. We suggest setting the following INCAR tags,

 KERNEL_TRUNCATION {
       LTRUNCATE_COULOMB_KERNEL = T
       IDIMENIONALITY_CUTOFF    = 2
       LCOARSEN_BEFORE_PAD      = T
       ISURFACE_NORMAL          = 3
 }