Update docs: angle_quartic

\documentclass[12pt]{article}

\begin{document}

$$

  E = K_2 (\theta - \theta_0)^2 + K_3 (\theta - \theta_0)^3 + K_4 (\theta - \theta_0)^4

$$

\end{document}

.. index:: angle\_style quartic

.. index:: angle_style quartic

angle\_style quartic command

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

angle_style quartic command

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

angle\_style quartic/omp command

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

angle_style quartic/omp command

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

Syntax

""""""

.. parsed-literal::

.. code-block:: LAMMPS

   angle_style quartic

""""""""

.. parsed-literal::

.. code-block:: LAMMPS

   angle_style quartic

   angle_coeff 1 129.1948 56.8726 -25.9442 -14.2221

The *quartic* angle style uses the potential

.. image:: Eqs/angle_quartic.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_2 (\theta - \theta_0)^2 + K_3 (\theta - \theta_0)^3 + K_4 (\theta - \theta_0)^4

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:

* theta0 (degrees)

* K2 (energy/radian\^2)

* K3 (energy/radian\^3)

* K4 (energy/radian\^4)

* :math:`\theta_0` (degrees)

* :math:`K_2` (energy/radian\^2)

* :math:`K_3` (energy/radian\^3)

* :math:`K_4` (energy/radian\^4)

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

internally; hence the units of K are in energy/radian\^2.

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

internally; hence the units of :math:`K` are in energy/radian\^2.

----------

:doc:`angle\_coeff <angle_coeff>`

**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 quartic command :h3

angle_style quartic/omp command :h3

[Syntax:]

angle_style quartic :pre

[Examples:]

angle_style quartic

angle_coeff 1 129.1948 56.8726 -25.9442 -14.2221 :pre

[Description:]

The {quartic} angle style uses the potential

:c,image(Eqs/angle_quartic.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:

theta0 (degrees)

K2 (energy/radian^2)

K3 (energy/radian^3)

K4 (energy/radian^4) :ul

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

internally; hence the units of K are in energy/radian^2.

: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

USER_MISC package.  See the "Build package"_Build_package.html doc

page for more info.

[Related commands:]

"angle_coeff"_angle_coeff.html

[Default:] none