.. index:: dihedral_style fourier

dihedral_style fourier command
==============================

dihedral_style fourier/intel command
====================================

dihedral_style fourier/omp command
==================================

Syntax
""""""

.. code-block:: LAMMPS

   dihedral_style fourier

Examples
""""""""

.. code-block:: LAMMPS

   dihedral_style fourier
   dihedral_coeff 1 3 -0.846200 3 0.0 7.578800 1 0 0.138000 2 -180.0

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

The *fourier* dihedral style uses the potential:

.. math::

   E = \sum_{i=1,m} K_i  [ 1.0 + \cos ( n_i \phi - d_i ) ]

The following coefficients must be defined for each dihedral type via the
:doc:`dihedral_coeff <dihedral_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:

* :math:`m` (integer >=1)
* :math:`K_1` (energy)
* :math:`n_1` (integer >= 0)
* :math:`d_1` (degrees)
* [...]
* :math:`K_m` (energy)
* :math:`n_m` (integer >= 0)
* :math:`d_m` (degrees)

----------

Styles with a *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 on the :doc:`Speed packages <Speed_packages>` doc
page.  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 GPU, USER-INTEL, KOKKOS,
USER-OMP and OPT packages, respectively.  They are only enabled if
LAMMPS was built with those packages.  See the :doc:`Build package <Build_package>` doc page for more info.

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

See the :doc:`Speed packages <Speed_packages>` doc page for more
instructions on how to use the accelerated styles effectively.

----------

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

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

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

:doc:`dihedral_coeff <dihedral_coeff>`

**Default:** none
