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angle_coeff command

Syntax:

angle_coeff N args 

Examples:

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

Description:

Specify the force field coefficients for one or more angle types. The number and meaning of the coefficients depends on the angle style. As described below, 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 asterik 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 asterik with no numeric values means all types from 1 to N. A leading asterik means all types from 1 to n (inclusive). A trailing asterik means all types from n to N (inclusive). A middle asterik means all types from m to n (inclusive).

Note that using 2 angle_coeff commands for the same angle type is perfectly valid. 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 asteriks should not be used since coefficients for all N types are 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 units of each coefficient are shown in parenthesis.


For style charmm, specify 4 coefficients:

Theta0 is specified in degrees, but LAMMPS converts it to radians internally; hence the units of K are in energy/radian^2.


For style class2, only coefficients for the Ea formula can be specified in the input script. These are the 4 coefficients:

Theta0 is specified in degrees, but LAMMPS converts it to radians internally; hence the units of K are in energy/radian^2.

Coefficients for the Ebb and Eba formulas must be specified in the data file.

For the Ebb formula, the coefficients are listed under a "BondBond Coeffs" heading and each line lists 3 coefficients:

For the Eba formula, the coefficients are listed under a "BondAngle Coeffs" heading and each line lists 4 coefficients:

The theta0 value in the Eba formula is not specified, since it is the same value from the Ea formula.


For style cosine, specify 1 coefficient:


For style harmonic, specify 2 coefficients:

Theta0 is specified in degrees, but LAMMPS converts it to radians internally; hence the units of K are in energy/radian^2.

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