# BOND

Section can be repeated.

Specifies the bond potential [Edit on GitHub]

## Keywords

- ATOMS

- CS

- K

- KIND

- R0

## Keyword descriptions

ATOMS: string[2]

  Usage: ATOMS {KIND1} {KIND2}

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

CS: real = 0.00000000E+000 [bohr^-1]

  Usage: CS {real}

  Defines the cubic stretch term. [Edit on GitHub]

K: real[ ] = [internal_cp2k]

  Usage: K {real}

  Defines the force constant of the potential. For MORSE potentials 2 numbers are expected. For QUARTIC potentials 3 numbers are expected. [Edit on GitHub]

KIND: enum = CHARMM

  Usage: KIND HARMONIC

  Valid values:

  - `HARMONIC` Functional Form (HARMONIC|G87): 1/2K(R-R0)^2

  - `CHARMM` Functional Form (CHARMM|AMBER): K*(R-R0)^2

  - `AMBER` Functional Form (CHARMM|AMBER): K*(R-R0)^2

  - `G87` Functional Form (HARMONIC|G87): 1/2K(R-R0)^2

  - `G96` Functional Form (G96): 1/4K(R^2-R0^2)^2

  - `QUARTIC` Functional Form (QUARTIC): (1/2K1+[1/3K2+1/4K3|R-R0|]*|R-R0|)(R-R0)^2

  - `MORSE` Functional Form (MORSE): K1*[(1-exp(-K2*(R-R0)))^2-1])

  - `CUBIC` Functional Form (CUBIC): K*(R-R0)^2*(1+cs*(R-R0)+7/12*(cs^2*(R-R0)^2))

  - `FUES` Functional Form (FUES): 1/2KR0^2*(1+R0/R*(R0/R-2))

  Define the kind of Bondpotential. [Edit on GitHub]

R0: real = [bohr]

  Usage: R0 {real}

  Defines the equilibrium distance. [Edit on GitHub]