# POISSON

Sets up the poisson resolutor. [Edit on GitHub]

Subsections

- EWALD
- IMPLICIT
- MT
- MULTIPOLE
- WAVELET

## Keywords

- PERIODIC

- POISSON_SOLVER

## Keyword descriptions

PERIODIC: enum = XYZ

  Usage: PERIODIC (x|y|z|xy|xz|yz|xyz|none)

  Valid values:

  - `X`

  - `Y`

  - `Z`

  - `XY`

  - `XZ`

  - `YZ`

  - `XYZ`

  - `NONE`

  Specify the directions in which PBC apply. Important notice, this only applies to the electrostatics. See the CELL section to specify the periodicity used for e.g. the pair lists. Typically the settings should be the same. [Edit on GitHub]

POISSON_SOLVER: enum = PERIODIC

  Aliases: POISSON ,PSOLVER

  Usage: POISSON_SOLVER char

  Valid values:

  - `PERIODIC` PERIODIC is only available for fully (3D) periodic systems.

  - `ANALYTIC` ANALYTIC is available for 0D, 1D and 2D periodic solutions using analytical green functions in the g space (slow convergence).

  - `MT` MT (Martyna Tuckermann) decoupling that interacts only with the nearest neighbor. Beware results are completely wrong if the cell is smaller than twice the cluster size (with electronic density). Available for 0D and 2D systems.

  - `MULTIPOLE` MULTIPOLE uses a scheme that fits the total charge with one gaussian per atom. Available only for cluster (0D) systems.

  - `WAVELET` WAVELET allows for 0D, 2D (but only PERIODIC XZ) and 3D systems. It does not require very large unit cells, only that the density goes to zero on the faces of the cell. The use of PREFERRED_FFT_LIBRARY FFTSG is required.

  - `IMPLICIT` IMPLICIT allows for 0D, 1D, 2D and 3D systems.

  References: Blchl1995, Martyna1999, Genovese2006, Genovese2007

  Specify which kind of solver to use to solve the Poisson equation. [Edit on GitHub]