forked from lijiext/lammps
104 lines
4.1 KiB
HTML
104 lines
4.1 KiB
HTML
<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 command
|
|
</H3>
|
|
<P><B>Syntax:</B>
|
|
</P>
|
|
<PRE>bond_style style args
|
|
</PRE>
|
|
<UL><LI>style = <I>none</I> or <I>hybrid</I> or <I>class2</I> or <I>fene</I> or <I>fene/expand</I> or <I>harmonic</I> or <I>morse</I> or <I>nonlinear</I> or <I>quartic</I>
|
|
</UL>
|
|
<PRE> args = none for any style except <I>hybrid</I>
|
|
<I>hybrid</I> args = list of one or more styles
|
|
</PRE>
|
|
<P><B>Examples:</B>
|
|
</P>
|
|
<PRE>bond_style harmonic
|
|
bond_style fene
|
|
bond_style hybrid harmonic fene
|
|
</PRE>
|
|
<P><B>Description:</B>
|
|
</P>
|
|
<P>Set the formula(s) LAMMPS uses to compute bond interactions between
|
|
pairs of atoms. In LAMMPS, a bond differs from a pairwise
|
|
interaction, which are set via the <A HREF = "pair_style.html">pair_style</A>
|
|
command. Bonds are defined between specified pairs of atoms and
|
|
remain in force for the duration of the simulation (unless the bond
|
|
breaks which is possible in some bond potentials). The list of bonded
|
|
atoms is read in by a <A HREF = "read_data.html">read_data</A> or
|
|
<A HREF = "read_restart.html">read_restart</A> command from a data or restart file.
|
|
By contrast, pair potentials are typically defined between all pairs
|
|
of atoms within a cutoff distance and the set of active interactions
|
|
changes over time.
|
|
</P>
|
|
<P>Hybrid models where bonds are computed using different bond potentials
|
|
can be setup using the <I>hybrid</I> bond style.
|
|
</P>
|
|
<P>The coefficients associated with a bond style can be specified in a
|
|
data or restart file or via the <A HREF = "bond_coeff.html">bond_coeff</A> command.
|
|
</P>
|
|
<P>All bond potentials store their coefficient data in binary restart
|
|
files which means bond_style and <A HREF = "bond_coeff.html">bond_coeff</A> commands
|
|
do not need to be re-specified in an input script that restarts a
|
|
simulation. See the <A HREF = "read_restart.html">read_restart</A> command for
|
|
details on how to do this. The one exception is that bond_style
|
|
<I>hybrid</I> only stores the list of sub-styles in the restart file; bond
|
|
coefficients need to be re-specified.
|
|
</P>
|
|
<P>IMPORTANT NOTE: When both a bond and pair style is defined, the
|
|
<A HREF = "special_bonds.html">special_bonds</A> command often needs to be used to
|
|
turn off (or weight) the pairwise interaction that would otherwise
|
|
exist between 2 bonded atoms.
|
|
</P>
|
|
<P>In the formulas listed for each bond style, <I>r</I> is the distance
|
|
between the 2 atoms in the bond.
|
|
</P>
|
|
<HR>
|
|
|
|
<P>Here is an alphabetic list of bond styles defined in LAMMPS. Click on
|
|
the style to display the formula it computes and coefficients
|
|
specified by the associated <A HREF = "bond_coeff.html">bond_coeff</A> command:
|
|
</P>
|
|
<UL><LI><A HREF = "bond_none.html">bond_style none</A> - turn off bonded interactions
|
|
<LI><A HREF = "bond_hybrid.html">bond_style hybrid</A> - define multiple styles of bond interactions
|
|
</UL>
|
|
<UL><LI><A HREF = "bond_class2.html">bond_style class2</A> - COMPASS (class 2) bond
|
|
<LI><A HREF = "bond_fene.html">bond_style fene</A> - FENE (finite-extensible non-linear elastic) bond
|
|
<LI><A HREF = "bond_fene_expand.html">bond_style fene/expand</A> - FENE bonds with variable size particles
|
|
<LI><A HREF = "bond_harmonic.html">bond_style harmonic</A> - harmonic bond
|
|
<LI><A HREF = "bond_morse.html">bond_style morse</A> - Morse bond
|
|
<LI><A HREF = "bond_nonlinear.html">bond_style nonlinear</A> - nonlinear bond
|
|
<LI><A HREF = "bond_quartic.html">bond_style quartic</A> - breakable quartic bond
|
|
</UL>
|
|
<HR>
|
|
|
|
<P><B>Restrictions:</B>
|
|
</P>
|
|
<P>Bond styles can only be set for atom styles that allow bonds to be
|
|
defined.
|
|
</P>
|
|
<P>Most bond styles are part of the "molecular" package. They are only
|
|
enabled if LAMMPS was built with that package. See the <A HREF = "Section_start.html#2_3">Making
|
|
LAMMPS</A> section for more info on packages. The
|
|
doc pages for individual bond potentials tell if it is part of a
|
|
package.
|
|
</P>
|
|
<P><B>Related commands:</B>
|
|
</P>
|
|
<P><A HREF = "bond_coeff.html">bond_coeff</A>, <A HREF = "delete_bonds.html">delete_bonds</A>
|
|
</P>
|
|
<P><B>Default:</B>
|
|
</P>
|
|
<P>bond_style none
|
|
</P>
|
|
</HTML>
|