- style = none or hybrid or charmm or class2 or cosine or cosine/squared or harmonic
angle_style harmonic angle_style charmm angle_style hybrid harmonic cosine
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.
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 full list of all angle styles are is on the Commands bond doc page.
- none - turn off angle interactions
- zero - topology but no interactions
- hybrid - define multiple styles of angle interactions
- charmm - CHARMM angle
- class2 - COMPASS (class 2) angle
- class2/p6 - COMPASS (class 2) angle expanded to 6th order
- cosine - angle with cosine term
- cosine/buck6d - same as cosine with Buckingham term between 1-3 atoms
- cosine/delta - angle with difference of cosines
- cosine/periodic - DREIDING angle
- cosine/shift - angle cosine with a shift
- cosine/shift/exp - cosine with shift and exponential term in spring constant
- cosine/squared - angle with cosine squared term
- dipole - angle that controls orientation of a point dipole
- fourier - angle with multiple cosine terms
- fourier/simple - angle with a single cosine term
- harmonic - harmonic angle
- quartic - angle with cubic and quartic terms
- sdk - harmonic angle with repulsive SDK pair style between 1-3 atoms
- table - tabulated by angle
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 Build package doc page for more info. The doc pages for individual bond potentials tell if it is part of a package.