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### angle_style cosine/periodic command

Syntax:

    angle_style cosine/periodic

Examples:

    angle_style cosine/periodic
    angle_coeff * 75.0 1 6

Description:

The cosine/periodic angle style uses the following potential, which is commonly used in the DREIDING force field, particularly for organometallic systems where n = 4 might be used for an octahedral complex and n = 3 might be used for a trigonal center:

where C, B and n are coefficients defined for each angle type.

See (Mayo) for a description of the DREIDING 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:

- C (energy)
- B = 1 or -1
- n = 1, 2, 3, 4, 5 or 6 for periodicity

Note that the prefactor C is specified and not the overall force constant K = C / n^2. When B = 1, it leads to a minimum for the linear geometry. When B = -1, it leads to a maximum for the linear geometry.

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

(Mayo) Mayo, Olfason, Goddard III, J Phys Chem, 94, 8897-8909 (1990).