fix_wiggle.html
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fix_wiggle.html
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			<H3>fix wiggle command
			</H3>
			<P><B>Syntax:</B>
			</P>
			<P>fix ID group-ID wiggle dim amplitude period
			</P>
			<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
			<LI>wiggle = style name of this fix command
			<LI>dim = <I>x</I> or <I>y</I> or <I>z</I>
			<LI>amplitude = size of oscillation (distance units)
			<LI>period = time of oscillation (time units)
			</UL>
			<P><B>Examples:</B>
			</P>
			<PRE>fix 1 frozen wiggle 3.0 0.5
			</PRE>
			<P><B>Description:</B>
			</P>
			<P>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 <I>dim</I> of movement is specified as
			is the <I>amplitude</I> and <I>period</I> of the oscillations. Each timestep
			the <I>dim</I> coordinate of each atom is set to
			</P>
			<PRE>coord = coord0 + A - A cos (omega * delta)
			</PRE>
			<P>where <I>coord0</I> is the coordinate at the time the fix was specified,
			<I>A</I> is the <I>amplitude</I>, <I>omega</I> is 2 PI / <I>period</I>, and <I>delta</I> is the
			elapsed time since the fix was specified. The velocity of the atom is
			set to the derivative of this expression.
			</P>
			<P><B>Restrictions:</B> none
			</P>
			<P><B>Related commands:</B> none
			</P>
			<P><B>Default:</B> none
			</P>
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