forked from lijiext/lammps
85 lines
2.9 KiB
HTML
85 lines
2.9 KiB
HTML
<HTML>
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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>
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</CENTER>
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<HR>
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<H3>bond_style harmonic/shift/cut command
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</H3>
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<H3>bond_style harmonic/shift/cut/omp command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>bond_style harmonic/shift/cut
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</PRE>
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<P><B>Examples:</B>
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</P>
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<PRE>bond_style harmonic/shift/cut
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bond_coeff 5 10.0 0.5 1.0
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>The <I>harmonic/shift/cut</I> bond style is a shifted harmonic bond that
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uses the potential
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</P>
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<CENTER><IMG SRC = "Eqs/bond_harmonic_shift_cut.jpg">
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</CENTER>
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<P>where r0 is the equilibrium bond distance, and rc the critical distance.
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The bond potential is zero for distances r > rc. The potential is -Umin
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at r0 and zero at rc. The spring constant is k = Umin / [ 2 (r0-rc)^2].
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</P>
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<P>The following coefficients must be defined for each bond type via the
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<A HREF = "bond_coeff.html">bond_coeff</A> command as in the example above, or in
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the data file or restart files read by the <A HREF = "read_data.html">read_data</A>
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or <A HREF = "read_restart.html">read_restart</A> commands:
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</P>
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<UL><LI>Umin (energy)
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<LI>r0 (distance)
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<LI>rc (distance)
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</UL>
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<HR>
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<P>Styles with a <I>cuda</I>, <I>gpu</I>, <I>intel</I>, <I>kk</I>, <I>omp</I>, or <I>opt</I> suffix are
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functionally the same as the corresponding style without the suffix.
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They have been optimized to run faster, depending on your available
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hardware, as discussed in <A HREF = "Section_accelerate.html">Section_accelerate</A>
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of the manual. The accelerated styles take the same arguments and
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should produce the same results, except for round-off and precision
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issues.
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</P>
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<P>These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
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KOKKOS, USER-OMP and OPT packages, respectively. They are only
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enabled if LAMMPS was built with those packages. See the <A HREF = "Section_start.html#start_3">Making
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LAMMPS</A> section for more info.
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</P>
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<P>You can specify the accelerated styles explicitly in your input script
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by including their suffix, or you can use the <A HREF = "Section_start.html#start_7">-suffix command-line
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switch</A> when you invoke LAMMPS, or you can
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use the <A HREF = "suffix.html">suffix</A> command in your input script.
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</P>
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<P>See <A HREF = "Section_accelerate.html">Section_accelerate</A> of the manual for
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more instructions on how to use the accelerated styles effectively.
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</P>
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<HR>
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<P><B>Restrictions:</B>
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</P>
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<P>This bond style can only be used if LAMMPS was built with the
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USER-MISC package. See the <A HREF = "Section_start.html#start_3">Making LAMMPS</A>
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section for more info on packages.
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</P>
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<P><B>Related commands:</B>
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</P>
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<P><A HREF = "bond_coeff.html">bond_coeff</A>, <A HREF = "delete_bonds.html">delete_bonds</A>,
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<A HREF = "bond_harmonic.html">bond_harmonic</A>,
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<A HREF = "bond_harmonicshift.html">bond_harmonicshift</A>
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</P>
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<P><B>Default:</B> none
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</P>
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</HTML>
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