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angle_quartic.txt
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.. index:: angle_style quartic
angle_style quartic command
===========================
angle_style quartic/omp command
===============================
Syntax
""""""
.. parsed-literal::
angle_style quartic
Examples
""""""""
.. parsed-literal::
angle_style quartic
angle_coeff 1 129.1948 56.8726 -25.9442 -14.2221
Description
"""""""""""
The *quartic* angle style uses the potential
.. image:: Eqs/angle_quartic.jpg
:align: center
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
: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)
Theta0 is specified in degrees, but LAMMPS converts it to radians
internally; hence the units of K are in energy/radian^2.
----------
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 angle 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:`angle_coeff <angle_coeff>`
**Default:** none
.. _lws: http://lammps.sandia.gov
.. _ld: Manual.html
.. _lc: Section_commands.html#comm
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