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Sat, Nov 23, 19:50
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rLAMMPS lammps
bond_hybrid.html
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<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 hybrid command
</H3>
<P><B>
Syntax:
</B>
</P>
<PRE>
bond_style hybrid style1 style2 ...
</PRE>
<UL><LI>
style1,style2 = list of one or more bond styles
</UL>
<P><B>
Examples:
</B>
</P>
<PRE>
bond_style hybrid harmonic fene
bond_coeff 1 harmonic 80.0 1.2
bond_coeff 2* fene 30.0 1.5 1.0 1.0
</PRE>
<P><B>
Description:
</B>
</P>
<P>
The
<I>
hybrid
</I>
style enables the use of multiple bond styles in one
simulation. A bond style is assigned to each bond type. For example,
bonds in a polymer flow (of bond type 1) could be computed with a
<I>
fene
</I>
potential and bonds in the wall boundary (of bond type 2) could
be computed with a
<I>
harmonic
</I>
potential. The assignment of bond type
to style is made via the
<A
HREF =
"bond_coeff.html"
>
bond_coeff
</A>
command or in
the data file.
</P>
<P>
In the bond_coeff commands, the name of a bond style must be added
after the bond type, with the remaining coefficients being those
appropriate to that style. In the example above, the 2 bond_coeff
commands set bonds of bond type 1 to be computed with a
<I>
harmonic
</I>
potential with coefficients 80.0, 1.2 for K, r0. All other bond types
(2-N) are computed with a
<I>
fene
</I>
potential with coefficients 30.0,
1.5, 1.0, 1.0 for K, R0, epsilon, sigma.
</P>
<P>
If bond coefficients are specified in the data file read via the
<A
HREF =
"read_data.html"
>
read_data
</A>
command, then the same rule applies.
E.g. "harmonic" or "fene" must be added after the bond type, for each
line in the "Bond Coeffs" section, e.g.
</P>
<PRE>
Bond Coeffs
</PRE>
<PRE>
1 harmonic 80.0 1.2
2 fene 30.0 1.5 1.0 1.0
...
</PRE>
<P>
A bond style of
<I>
none
</I>
with no additional coefficients can be used in
place of a bond style, either in a input script bond_coeff command or
in the data file, if you desire to turn off interactions for specific
bond types.
</P>
<HR>
<P><B>
Restrictions:
</B>
</P>
<P>
This bond style can only be used if LAMMPS was built with the
MOLECULE package (which it is by default). See the
<A
HREF =
"Section_start.html#start_3"
>
Making
LAMMPS
</A>
section for more info on packages.
</P>
<P>
Unlike other bond styles, the hybrid bond style does not store bond
coefficient info for individual sub-styles in a
<A
HREF =
"restart.html"
>
binary restart
files
</A>
. Thus when retarting a simulation from a restart
file, you need to re-specify bond_coeff commands.
</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>
none
</P>
</HTML>
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