# FORCEFIELD

Section specifying information regarding how to set up properly a force_field for the classical calculations. [Edit on GitHub]

Subsections

- BEND
- BOND
- CHARGE
- CHARGES
- DIPOLE
- IMPROPER
- NONBONDED
- NONBONDED14
- OPBEND
- QUADRUPOLE
- SHELL
- SPLINE
- TORSION

## Keywords

- DO_ELECTROSTATICS

- DO_NONBONDED

- EI_SCALE14

- IGNORE_MISSING_CRITICAL_PARAMS

- MULTIPLE_POTENTIAL

- PARMTYPE

- PARM_FILE_NAME

- SHIFT_CUTOFF

- VDW_SCALE14

- ZBL_SCATTERING

## Keyword descriptions

DO_ELECTROSTATICS: logical = T

  Lone keyword: `T`

  Usage: DO_ELECTROSTATICS T

  Controls the computation of all the real-space (short-range) electrostatics interactions. This does not affect the QM/MM electrostatic coupling when turned off. [Edit on GitHub]

DO_NONBONDED: logical = T

  Lone keyword: `T`

  Usage: DO_NONBONDED T

  Controls the computation of all the real-space (short-range) nonbonded interactions. This also includes the real-space corrections for excluded or scaled 1-2, 1-3 and 1-4 interactions. When set to F, the neighborlists are not created and all interactions that depend on them are not computed. [Edit on GitHub]

EI_SCALE14: real = 0.00000000E+000

  Usage: EI_SCALE14 1.0

  Scaling factor for the electrostatics 1-4 [Edit on GitHub]

IGNORE_MISSING_CRITICAL_PARAMS: logical = F

  Lone keyword: `T`

  Usage: IGNORE_MISSING_CRITICAL_PARAMS .TRUE.

  Do not abort when critical force-field parameters are missing. CP2K will run as if the terms containing the missing parameters are zero. [Edit on GitHub]

MULTIPLE_POTENTIAL: logical = F

  Lone keyword: `T`

  Usage: MULTIPLE_POTENTIAL T

  Enables the possibility to define NONBONDED and NONBONDED14 as a sum of different kinds of potential. Useful for piecewise defined potentials. [Edit on GitHub]

PARMTYPE: enum = OFF

  Usage: PARMTYPE {OFF,CHM,G87,G96}

  Valid values:

  - `OFF` Provides force field parameters through the input file

  - `CHM` Provides force field parameters through an external file with CHARMM format

  - `G87` Provides force field parameters through an external file with GROMOS 87 format

  - `G96` Provides force field parameters through an external file with GROMOS 96 format

  - `AMBER` Provides force field parameters through an external file with AMBER format (from v.8 on)

  Define the kind of torsion potential [Edit on GitHub]

PARM_FILE_NAME: string

  Usage: PARM_FILE_NAME {FILENAME}

  Mentions: ⭐QM/MM with Built-in Force Field

  Specifies the filename that contains the parameters of the FF. [Edit on GitHub]

SHIFT_CUTOFF: logical = T

  Usage: SHIFT_CUTOFF <LOGICAL>

  Add a constant energy shift to the real-space non-bonding interactions (both Van der Waals and electrostatic) such that the energy at the cutoff radius is zero. This makes the non-bonding interactions continuous at the cutoff. [Edit on GitHub]

VDW_SCALE14: real = 1.00000000E+000

  Usage: VDW_SCALE14 1.0

  Scaling factor for the VDW 1-4 [Edit on GitHub]

ZBL_SCATTERING: logical = F

  Lone keyword: `T`

  Usage: ZBL_SCATTERING T

  A short range repulsive potential is added, to simulate collisions and scattering. [Edit on GitHub]