.. index:: bond_style class2

bond_style class2 command
=========================

bond_style class2/omp command
=============================

Syntax
""""""

.. parsed-literal::

   bond_style class2

Examples
""""""""

.. parsed-literal::

   bond_style class2
   bond_coeff 1 1.0 100.0 80.0 80.0

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

The *class2* bond style uses the potential

.. image:: Eqs/bond_class2.jpg
   :align: center

where r0 is the equilibrium bond distance.

See :ref:`(Sun) <bond-Sun>` for a description of the COMPASS class2 force field.

The following coefficients must be defined for each bond type via the
:doc:`bond_coeff <bond_coeff>` command as in the example above, or in
the data file or restart files read by the :doc:`read_data <read_data>`
or :doc:`read_restart <read_restart>` commands:

* R0 (distance)
* K2 (energy/distance^2)
* K3 (energy/distance^3)
* K4 (energy/distance^4)


----------


Styles with a *cuda*\ , *gpu*\ , *intel*\ , *kk*\ , *omp*\ , or *opt* 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 :doc:`Section_accelerate <Section_accelerate>`
of the manual.  The accelerated styles take the same arguments and
should produce the same results, except for round-off and precision
issues.

These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
KOKKOS, USER-OMP and OPT packages, respectively.  They are only
enabled if LAMMPS was built with those packages.  See the :ref:`Making LAMMPS <start_3>` section for more info.

You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the :ref:`-suffix command-line switch <start_7>` when you invoke LAMMPS, or you can
use the :doc:`suffix <suffix>` command in your input script.

See :doc:`Section_accelerate <Section_accelerate>` of the manual for
more instructions on how to use the accelerated styles effectively.


----------


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


This bond style can only be used if LAMMPS was built with the CLASS2
package.  See the :ref:`Making LAMMPS <start_3>` section
for more info on packages.

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

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

**Default:** none


----------


.. _bond-Sun:



**(Sun)** Sun, J Phys Chem B 102, 7338-7364 (1998).


.. _lws: http://lammps.sandia.gov
.. _ld: Manual.html
.. _lc: Section_commands.html#comm