# TORSION

Section can be repeated.

Specifies the torsion potential of the MM system. [Edit on GitHub]

## Keywords

- ATOMS

- K

- KIND

- M

- PHI0

## Keyword descriptions

ATOMS: string[4]

  Usage: ATOMS {KIND1} {KIND2} {KIND3} {KIND4}

  Defines the atomic kinds involved in the tors. [Edit on GitHub]

K: real = [hartree]

  Usage: K {real}

  Defines the force constant of the potential [Edit on GitHub]

KIND: enum = CHARMM

  Usage: KIND CHARMM

  Valid values:

  - `CHARMM` Functional Form (CHARMM|G87|G96|AMBER): K * [ 1 + cos[M*PHI - PHI0]]

  - `G87` Functional Form (CHARMM|G87|G96|AMBER): K * [ 1 + cos[M*PHI - PHI0]]

  - `G96` Functional Form (CHARMM|G87|G96|AMBER): K * [ 1 + cos[M*PHI - PHI0]]

  - `AMBER` Functional Form (CHARMM|G87|G96|AMBER): K * [ 1 + cos[M*PHI - PHI0]]

  - `OPLS` Functional Form: K / 2 * [ 1 + (-1)^(M-1) * cos[M*PHI]]

  Define the kind of torsion potential [Edit on GitHub]

M: integer

  Usage: M {integer}

  Defines the multiplicity of the potential. [Edit on GitHub]

PHI0: real = 0.00000000E+000 [rad]

  Usage: PHI0 {real}

  Defines the phase of the potential. [Edit on GitHub]