.. index:: bond_style harmonic/shift/cut

bond_style harmonic/shift/cut command
=====================================

bond_style harmonic/shift/cut/omp command
=========================================

Syntax
""""""

.. parsed-literal::

   bond_style harmonic/shift/cut

Examples
""""""""

.. parsed-literal::

   bond_style harmonic/shift/cut
   bond_coeff 5 10.0 0.5 1.0

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

The *harmonic/shift/cut* bond style is a shifted harmonic bond that
uses the potential

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

where r0 is the equilibrium bond distance, and rc the critical distance.
The bond potential is zero for distances r > rc. The potential is -Umin
at r0 and zero at rc. The spring constant is k = Umin / [ 2 (r0-rc)^2].

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:

* Umin (energy)
* r0 (distance)
* rc (distance)


----------


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
USER-MISC 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>`,
:doc:`bond_harmonic <bond_harmonic>`,
:doc:`bond_harmonicshift <bond_harmonicshift>`

**Default:** none


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