.. index:: bond_style hybrid

bond_style hybrid command
=========================

Syntax
""""""

.. code-block:: LAMMPS

   bond_style hybrid style1 style2 ...

* style1,style2 = list of one or more bond styles

Examples
""""""""

.. code-block: LAMMPS

   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

Description
"""""""""""

The *hybrid* 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
*fene* potential and bonds in the wall boundary (of bond type 2) could
be computed with a *harmonic* potential.  The assignment of bond type
to style is made via the :doc:`bond_coeff <bond_coeff>` command or in
the data file.

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 *harmonic*
potential with coefficients 80.0, 1.2 for :math:`K`, :math:`r_0`.  All other bond types
(2-N) are computed with a *fene* potential with coefficients 30.0,
1.5, 1.0, 1.0 for :math:`K`, :math:`R_0`, :math:`\epsilon`, :math:`\sigma`.

If bond coefficients are specified in the data file read via the
:doc:`read_data <read_data>` 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.

.. parsed-literal::

   Bond Coeffs

   1 harmonic 80.0 1.2
   2 fene 30.0 1.5 1.0 1.0
   ...

A bond style of *none* 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.

----------

Restrictions
""""""""""""

This bond style can only be used if LAMMPS was built with the MOLECULE
package.  See the :doc:`Build package <Build_package>` page for more
info.

Unlike other bond styles, the hybrid bond style does not store bond
coefficient info for individual sub-styles in a :doc:`binary restart files <restart>`.  Thus when restarting a simulation from a restart
file, you need to re-specify bond_coeff commands.

Related commands
""""""""""""""""

:doc:`bond_coeff <bond_coeff>`, :doc:`delete_bonds <delete_bonds>`

Default
"""""""

none
