lammps/doc/fix_wiggle.txt

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fix wiggle command :h3

[Syntax:]

fix ID group-ID wiggle dim amplitude period

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 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.

[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