# WALLS

Enables Walls for the QM box. This can be used to avoid that QM atoms move out of the QM box. [Edit on GitHub]

## Keywords

- K

- TYPE

- WALL_SKIN

## Keyword descriptions

K: real = [internal_cp2k]

  Usage: K <real>

  Specify the value of the the force constant for the quadratic wall [Edit on GitHub]

TYPE: enum = REFLECTIVE

  Usage: TYPE REFLECTIVE

  Valid values:

  - `NONE` No Wall around QM box

  - `REFLECTIVE` Reflective Wall around QM box

  - `QUADRATIC` Quadratic Wall around QM box

  Specifies the type of wall [Edit on GitHub]

WALL_SKIN: real[3] = 5.00000000E-001 5.00000000E-001 5.00000000E-001 [angstrom]

  Usage: WALL_SKIN <real> <real> <real>

  Specify the value of the skin of the Wall in each dimension. The wall’s effect is felt when atoms fall within the skin of the Wall. [Edit on GitHub]