# angle_style cross command¶

## Syntax¶

angle_style cross


## Examples¶

angle_style cross
angle_coeff 1 200.0 100.0 100.0 1.25 1.25 107.0


## Description¶

The cross angle style uses a potential that couples the bond stretches of a bend with the angle stretch of that bend:

$E = K_{SS} \left(r_{12}-r_{12,0}\right)\left(r_{32}-r_{32,0}\right) + K_{BS0}\left(r_{12}-r_{12,0}\right)\left(\theta-\theta_0\right) + K_{BS1}\left(r_{32}-r_{32,0}\right)\left(\theta-\theta_0\right)$

where $$r_{12,0}$$ is the rest value of the bond length between atom 1 and 2, $$r_{32,0}$$ is the rest value of the bond length between atom 3 and 2, and $$\theta_0$$ is the rest value of the angle. $$K_{SS}$$ is the force constant of the bond stretch-bond stretch term and $$K_{BS0}$$ and $$K_{BS1}$$ are the force constants of the bond stretch-angle stretch terms.

The following coefficients must be defined for each angle type via the angle_coeff command as in the example above, or in the data file or restart files read by the read_data or read_restart commands:

• $$K_{SS}$$ (energy/distance^2)

• $$K_{BS0}$$ (energy/distance)

• $$K_{BS1}$$ (energy/distance)

• $$r_{12,0}$$ (distance)

• $$r_{32,0}$$ (distance)

• $$\theta_0$$ (degrees)

$$\theta_0$$ is specified in degrees, but LAMMPS converts it to radians internally; hence the $$K_{BS0}$$ and $$K_{BS1}$$ are effectively energy/distance per radian.

## Restrictions¶

This angle style can only be used if LAMMPS was built with the YAFF package. See the Build package doc page for more info.

none