LAMMPS WWW Site - LAMMPS Documentation - LAMMPS Commands

### angle_coeff command

Syntax:

    angle_coeff N args

- N = angle type (see asterisk form below)
- args = coefficients for one or more angle types

Examples:

    angle_coeff 1 300.0 107.0
    angle_coeff * 5.0
    angle_coeff 2*10 5.0

Description:

Specify the angle force field coefficients for one or more angle types. The number and meaning of the coefficients depends on the angle style. Angle coefficients can also be set in the data file read by the read_data command or in a restart file.

N can be specified in one of two ways. An explicit numeric value can be used, as in the 1st example above. Or a wild-card asterisk can be used to set the coefficients for multiple angle types. This takes the form "*" or "*n" or "n*" or "m*n". If N = the number of angle types, then an asterisk with no numeric values means all types from 1 to N. A leading asterisk means all types from 1 to n (inclusive). A trailing asterisk means all types from n to N (inclusive). A middle asterisk means all types from m to n (inclusive).

Note that using an angle_coeff command can override a previous setting for the same angle type. For example, these commands set the coeffs for all angle types, then overwrite the coeffs for just angle type 2:

    angle_coeff * 200.0 107.0 1.2
    angle_coeff 2 50.0 107.0

A line in a data file that specifies angle coefficients uses the exact same format as the arguments of the angle_coeff command in an input script, except that wild-card asterisks should not be used since coefficients for all N types must be listed in the file. For example, under the "Angle Coeffs" section of a data file, the line that corresponds to the 1st example above would be listed as

    1 300.0 107.0

The angle_style class2 is an exception to this rule, in that an additional argument is used in the input script to allow specification of the cross-term coefficients. See its doc page for details.

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:

- angle_style none - turn off angle 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

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.

Restrictions:

This command must come after the simulation box is defined by a read_data, read_restart, or create_box command.

An angle style must be defined before any angle coefficients are set, either in the input script or in a data file.

Related commands:

angle_style

Default: none