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### fix wiggle command

Syntax:

    fix ID group-ID wiggle dim amplitude period

- ID, group-ID are documented in fix command
- wiggle = style name of this fix command
- dim = x or y or z
- amplitude = size of oscillation (distance units)
- period = time of oscillation (time units)

Examples:

    fix 1 frozen wiggle y 3.0 0.5

Description:

Move a group of atoms in a sinusoidal oscillation. This is useful in granular simulations when boundary atoms are wiggled to induce packing of the dynamic atoms. The dimension dim of movement is specified as is the amplitude and period of the oscillations. Each timestep the dim coordinate of each atom is set to

    coord = coord0 + A - A cos (omega * delta)

where coord0 is the coordinate at the time the fix was specified, A is the amplitude, omega is 2 PI / period, and delta is the elapsed time since the fix was specified. The velocity of the atom is set to the derivative of this expression.

Note that if a value of A > 0 is specified, each wiggling atom does not oscillate around its initial position, but moves entirely in the positive direction relative to its initial position. This is so that its initial velocity will be 0.0.

Restart, fix_modify, output, run start/stop, minimize info:

No information about this fix is written to binary restart files. None of the fix_modify options are relevant to this fix. No global scalar or vector or per-atom quantities are stored by this fix for access by various output commands. No parameter of this fix can be used with the start/stop keywords of the run command. This fix is not invoked during energy minimization.

Restrictions: none

Related commands: none

Default: none