\(\renewcommand{\AA}{\text{Å}}\)

angle_style cross command

Accelerator Variants: cross/kk, cross/omp

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.

Styles with a gpu, intel, kk, omp, or opt suffix are functionally the same as the corresponding style without the suffix. They have been optimized to run faster, depending on your available hardware, as discussed on the Accelerator packages page. The accelerated styles take the same arguments and should produce the same results, except for round-off and precision issues.

These accelerated styles are part of the GPU, INTEL, KOKKOS, OPENMP, and OPT packages, respectively. They are only enabled if LAMMPS was built with those packages. See the Build package page for more info.

You can specify the accelerated styles explicitly in your input script by including their suffix, or you can use the -suffix command-line switch when you invoke LAMMPS, or you can use the suffix command in your input script.

See the Accelerator packages page for more instructions on how to use the accelerated styles effectively.

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