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### angle_style charmm command

Syntax:

    angle_style charmm

Examples:

    angle_style charmm
    angle_coeff 1 300.0 107.0 50.0 3.0

Description:

The charmm angle style uses the potential

with an additional Urey_Bradley term based on the distance r between the 1st and 3rd atoms in the angle. K, theta0, Kub, and Rub are coefficients defined for each angle type.

See (MacKerell) for a description of the CHARMM force field.

The following coefficients must be defined for each angle type via the angle_coeff command as in the example above, or in the data file or restart files read by the read_data or read_restart commands:

- K (energy/radian^2)
- theta0 (degrees)
- K_ub (energy/distance^2)
- r_ub (distance)

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

Restrictions:

This angle style can only be used if LAMMPS was built with the "molecular" package (which it is by default). See the Making LAMMPS section for more info on packages.

Related commands:

angle_coeff

Default: none

(MacKerell) MacKerell, Bashford, Bellott, Dunbrack, Evanseck, Field, Fischer, Gao, Guo, Ha, et al, J Phys Chem, 102, 3586 (1998).