2011-08-09 06:50:30 +08:00
|
|
|
<HTML>
|
|
|
|
|
<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>
|
2011-12-01 23:35:32 +08:00
|
|
|
<H3>bond_style harmonic/shift/omp command
|
|
|
|
|
</H3>
|
2011-08-09 06:50:30 +08:00
|
|
|
<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>
|
2011-12-01 23:35:32 +08:00
|
|
|
<HR>
|
|
|
|
|
|
2011-12-14 04:35:35 +08:00
|
|
|
<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">Section_accelerate</A> of the
|
|
|
|
|
manual. The accelerated styles take the same arguments and should
|
|
|
|
|
produce the same results, except for round-off and precision issues.
|
2011-12-01 23:35:32 +08:00
|
|
|
</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
|
2012-01-28 07:39:14 +08:00
|
|
|
by including their suffix, or you can use the <A HREF = "Section_start.html#start_7">-suffix command-line
|
2011-12-01 23:35:32 +08:00
|
|
|
switch</A> when you invoke LAMMPS, or you can
|
|
|
|
|
use the <A HREF = "suffix.html">suffix</A> command in your input script.
|
|
|
|
|
</P>
|
2011-12-14 04:35:35 +08:00
|
|
|
<P>See <A HREF = "Section_accelerate.html">Section_accelerate</A> of the manual for
|
|
|
|
|
more instructions on how to use the accelerated styles effectively.
|
2011-12-01 23:35:32 +08:00
|
|
|
</P>
|
|
|
|
|
<HR>
|
|
|
|
|
|
2011-08-09 06:50:30 +08:00
|
|
|
<P><B>Restrictions:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<P>This bond style can only be used if LAMMPS was built with the
|
2011-08-27 02:53:00 +08:00
|
|
|
USER-MISC package. See the <A HREF = "Section_start.html#start_3">Making LAMMPS</A>
|
|
|
|
|
section for more info on packages.
|
2011-08-09 06:50:30 +08:00
|
|
|
</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>
|
