angle_style command

Syntax

angle_style style

style = none or hybrid or charmm or class2 or cosine or cosine/squared or harmonic

Examples

angle_style harmonic
angle_style charmm
angle_style hybrid harmonic cosine

Description

Set the formula(s) LAMMPS uses to compute angle interactions between triplets of atoms, which remain in force for the duration of the simulation. The list of angle triplets is read in by a read_data or read_restart command from a data or restart file.

Hybrid models where angles are computed using different angle potentials can be setup using the hybrid angle style.

The coefficients associated with a angle style can be specified in a data or restart file or via the angle_coeff command.

All angle potentials store their coefficient data in binary restart files which means angle_style and angle_coeff commands do not need to be re-specified in an input script that restarts a simulation. See the read_restart command for details on how to do this. The one exception is that angle_style hybrid only stores the list of sub-styles in the restart file; angle coefficients need to be re-specified.

Note

When both an angle and pair style is defined, the special_bonds command often needs to be used to turn off (or weight) the pairwise interaction that would otherwise exist between 3 bonded atoms.

In the formulas listed for each angle style, theta is the angle between the 3 atoms in the angle.

Here is an alphabetic list of angle styles defined in LAMMPS. Click on the style to display the formula it computes and coefficients specified by the associated angle_coeff command.

Note that there are also additional angle styles submitted by users which are included in the LAMMPS distribution. The list of these with links to the individual styles are given in the angle section of this page.

angle_style none - turn off angle interactions
angle_style zero - topology but no interactions
angle_style hybrid - define multiple styles of angle interactions
angle_style charmm - CHARMM angle
angle_style class2 - COMPASS (class 2) angle
angle_style cosine - cosine angle potential
angle_style cosine/delta - difference of cosines angle potential
angle_style cosine/periodic - DREIDING angle
angle_style cosine/squared - cosine squared angle potential
angle_style harmonic - harmonic angle
angle_style table - tabulated by angle

Restrictions

Angle styles can only be set for atom_styles that allow angles to be defined.

Most angle styles are part of the MOLECULE package. They are only enabled if LAMMPS was built with that package. See the Making LAMMPS section for more info on packages. The doc pages for individual bond potentials tell if it is part of a package.

Default

angle_style none