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:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)

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fix wiggle command :h3

[Syntax:]

fix ID group-ID wiggle dim amplitude period :pre

ID, group-ID are documented in "fix"_fix.html 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) :ul

[Examples:]

fix 1 frozen wiggle y 3.0 0.5 :pre

[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) :pre

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"_restart.html.  None of the "fix_modify"_fix_modify.html 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"_Section_howto.html#4_15.  No parameter of this fix can be
used with the {start/stop} keywords of the "run"_run.html command.
This fix is not invoked during "energy minimization"_minimize.html.

[Restrictions:] none

[Related commands:] none

[Default:] none
