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_{S S} (r_{12} - r_{12, 0}) (r_{32} - r_{32, 0}) + K_{B S 0} (r_{12} - r_{12, 0}) (θ - θ_{0}) + K_{B S 1} (r_{32} - r_{32, 0}) (θ - θ_{0})

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 $θ_{0}$ is the rest value of the angle. $K_{S S}$ is the force constant of the bond stretch-bond stretch term and $K_{B S 0}$ and $K_{B S 1}$ 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:

$K_{S S}$ (energy/distance^2)
$K_{B S 0}$ (energy/distance)
$K_{B S 1}$ (energy/distance)
$r_{12, 0}$ (distance)
$r_{32, 0}$ (distance)
$θ_{0}$ (degrees)

$θ_{0}$ is specified in degrees, but LAMMPS converts it to radians internally; hence the $K_{B S 0}$ and $K_{B S 1}$ 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.

Default

none