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<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
</CENTER>
<HR>
<H3>bond_style harmonic/shift command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>bond_style harmonic/shift
</PRE>
<P><B>Examples:</B>
</P>
<PRE>bond_style harmonic/shift
bond_coeff 5 10.0 0.5 1.0
</PRE>
<P><B>Description:</B>
</P>
<P>The <I>harmonic/shift</I> bond style is a shifted harmonic bond that uses
the potential
</P>
<CENTER><IMG SRC = "Eqs/bond_harmonic_shift.jpg">
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<P>where r0 is the equilibrium bond distance, and rc the critical distance.
The potential is -Umin at r0 and zero at rc. The spring constant is
k = Umin / [ 2 (r0-rc)^2].
</P>
<P>The following coefficients must be defined for each bond type via the
<A HREF = "bond_coeff.html">bond_coeff</A> command as in the example above, or in
the data file or restart files read by the <A HREF = "read_data.html">read_data</A>
or <A HREF = "read_restart.html">read_restart</A> commands:
</P>
<UL><LI>Umin (energy)
</UL>
<UL><LI>r0 (distance)
</UL>
<UL><LI>rc (distance)
</UL>
<P><B>Restrictions:</B>
</P>
<P>This bond style can only be used if LAMMPS was built with the
"user-misc" package. See the <A HREF = "Section_start.html#2_3">Making LAMMPS</A>
section for more info on packages.
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "bond_coeff.html">bond_coeff</A>, <A HREF = "delete_bonds.html">delete_bonds</A>,
<A HREF = "bond_harmonic.html">bond_harmonic</A>
</P>
<P><B>Default:</B> none
</P>
</HTML>
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