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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>
<H3>bond_style harmonic/shift/omp 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">
</CENTER>
<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>
<HR>
<P>Styles with a <I>cuda</I>, <I>gpu</I>, <I>omp</I>, or <I>opt</I> suffix are functionally
the same as the corresponding style without the suffix. They have
been optimized to run faster, depending on your available hardware,
as discussed in <A HREF = "Section_accelerate.html">this section</A> of the manual.
The accelerated styles take the same arguments and should produce the
same results, except for round-off and precision issues.
</P>
<P>These accelerated styles are part of the USER-CUDA, GPU, USER-OMP and OPT
packages, respectively. They are only enabled if LAMMPS was built with
those packages. See the <A HREF = "Section_start.html#start_3">Making LAMMPS</A>
section for more info.
</P>
<P>You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the <A HREF = "Section_start.html#start_6">-suffix command-line
switch</A> when you invoke LAMMPS, or you can
use the <A HREF = "suffix.html">suffix</A> command in your input script.
</P>
<P>See <A HREF = "Section_accelerate.html">this section</A> of the manual for more
instructions on how to use the accelerated styles effectively.
</P>
<HR>
<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#start_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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