\(\renewcommand{\AA}{\text{Å}}\)

# angle_style command¶

## Syntax¶

```
angle_style style
```

style =

*none*or*zero*or*hybrid*or*amoeba*or*charmm*or*class2*or*class2/p6*or*cosine*or*cosine/buck6d*or*cosine/delta*or*cosine/periodic*or*cosine/shift*or*cosine/shift/exp*or*cosine/squared*or*cross*or*dipole*or*fourier*or*fourier/simple*or*gaussian*or*harmonic*or*lepton*or*mm3*or*quartic*or*spica*or*table*

## 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.

Click on the style to display the formula it computes, any additional arguments specified in the angle_style command, and coefficients specified by the associated angle_coeff command.

There are also additional accelerated pair styles included in the LAMMPS distribution for faster performance on CPUs, GPUs, and KNLs. The individual style names on the Commands angle page are followed by one or more of (g,i,k,o,t) to indicate which accelerated styles exist.

none - turn off angle interactions

zero - topology but no interactions

hybrid - define multiple styles of angle interactions

amoeba - AMOEBA angle

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

cross - cross term coupling angle and bond lengths

dipole - angle that controls orientation of a point dipole

fourier - angle with multiple cosine terms

fourier/simple - angle with a single cosine term

gaussian - multi-centered Gaussian-based angle potential

harmonic - harmonic angle

lepton - angle potential from evaluating a string

mesocnt - piecewise harmonic and linear angle for bending-buckling of nanotubes

mm3 - anharmonic angle

quartic - angle with cubic and quartic terms

spica - harmonic angle with repulsive SPICA pair style between 1-3 atoms

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 Build package page for more info. The doc pages for individual bond potentials tell if it is part of a package.

## Default¶

```
angle_style none
```