Update docs: angle_cosine_delta

\documentclass[12pt]{article}

\begin{document}

$$

  E = K [1 - \cos(\theta - \theta_0)]

$$

\end{document}

.. index:: angle\_style cosine/delta

.. index:: angle_style cosine/delta

angle\_style cosine/delta command

=================================

angle_style cosine/delta command

================================

angle\_style cosine/delta/omp command

=====================================

angle_style cosine/delta/omp command

====================================

Syntax

""""""

.. parsed-literal::

.. code-block:: LAMMPS

   angle_style cosine/delta

""""""""

.. parsed-literal::

.. code-block:: LAMMPS

   angle_style cosine/delta

   angle_coeff 2\*4 75.0 100.0

   angle_coeff 2*4 75.0 100.0

Description

"""""""""""

The *cosine/delta* angle style uses the potential

.. image:: Eqs/angle_cosine_delta.jpg

   :align: center

.. math::

where theta0 is the equilibrium value of the angle, and K is a

prefactor.  Note that the usual 1/2 factor is included in K.

   E = K [1 - \cos(\theta - \theta_0)]

where :math:`\theta_0` is the equilibrium value of the angle, and :math:`K` is a

prefactor.  Note that the usual 1/2 factor is included in :math:`K`.

The following coefficients must be defined for each angle type via the

:doc:`angle\_coeff <angle_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:

* K (energy)

* theta0 (degrees)

* :math:`K` (energy)

* :math:`\theta_0` (degrees)

Theta0 is specified in degrees, but LAMMPS converts it to radians

:math:`\theta_0` is specified in degrees, but LAMMPS converts it to radians

internally.

:doc:`angle\_coeff <angle_coeff>`, :doc:`angle\_style cosine/squared <angle_cosine_squared>`

**Default:** none

.. _lws: http://lammps.sandia.gov

.. _ld: Manual.html

.. _lc: Commands_all.html

"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)

:link(ld,Manual.html)

:link(lc,Commands_all.html)

:line

angle_style cosine/delta command :h3

angle_style cosine/delta/omp command :h3

[Syntax:]

angle_style cosine/delta :pre

[Examples:]

angle_style cosine/delta

angle_coeff 2*4 75.0 100.0 :pre

[Description:]

The {cosine/delta} angle style uses the potential

:c,image(Eqs/angle_cosine_delta.jpg)

where theta0 is the equilibrium value of the angle, and K is a

prefactor.  Note that the usual 1/2 factor is included in K.

The following coefficients must be defined for each angle type via the

"angle_coeff"_angle_coeff.html command as in the example above, or in

the data file or restart files read by the "read_data"_read_data.html

or "read_restart"_read_restart.html commands:

K (energy)

theta0 (degrees) :ul

Theta0 is specified in degrees, but LAMMPS converts it to radians

internally.

:line

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 "Speed packages"_Speed_packages.html 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 "Build

package"_Build_package.html 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 "-suffix command-line

switch"_Run_options.html when you invoke LAMMPS, or you can use the

"suffix"_suffix.html command in your input script.

See the "Speed packages"_Speed_packages.html doc page for more

instructions on how to use the accelerated styles effectively.

:line

[Restrictions:]

This angle style can only be used if LAMMPS was built with the

MOLECULE package.  See the "Build package"_Build_package.html doc page

for more info.

[Related commands:]

"angle_coeff"_angle_coeff.html, "angle_style

cosine/squared"_angle_cosine_squared.html

[Default:] none