forked from lijiext/lammps
94 lines
2.5 KiB
Plaintext
94 lines
2.5 KiB
Plaintext
.. index:: angle_style quartic
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angle_style quartic command
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===========================
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angle_style quartic/omp command
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===============================
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Syntax
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""""""
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.. parsed-literal::
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angle_style quartic
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Examples
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""""""""
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.. parsed-literal::
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angle_style quartic
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angle_coeff 1 129.1948 56.8726 -25.9442 -14.2221
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Description
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"""""""""""
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The *quartic* angle style uses the potential
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.. image:: Eqs/angle_quartic.jpg
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:align: center
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where theta0 is the equilibrium value of the angle, and K is a
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prefactor. Note that the usual 1/2 factor is included in K.
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The following coefficients must be defined for each angle type via the
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:doc:`angle_coeff <angle_coeff>` command as in the example above, or in
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the data file or restart files read by the :doc:`read_data <read_data>`
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or :doc:`read_restart <read_restart>` commands:
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* theta0 (degrees)
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* K2 (energy/radian^2)
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* K3 (energy/radian^3)
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* K4 (energy/radian^4)
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Theta0 is specified in degrees, but LAMMPS converts it to radians
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internally; hence the units of K are in energy/radian^2.
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----------
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Styles with a *cuda*, *gpu*, *intel*, *kk*, *omp*, or *opt* suffix are
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functionally the same as the corresponding style without the suffix.
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They have been optimized to run faster, depending on your available
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hardware, as discussed in :doc:`Section_accelerate <Section_accelerate>`
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of the manual. The accelerated styles take the same arguments and
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should produce the same results, except for round-off and precision
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issues.
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These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
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KOKKOS, USER-OMP and OPT packages, respectively. They are only
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enabled if LAMMPS was built with those packages. See the :ref:`Making LAMMPS <start_3>` section for more info.
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You can specify the accelerated styles explicitly in your input script
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by including their suffix, or you can use the :ref:`-suffix command-line switch <start_7>` when you invoke LAMMPS, or you can
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use the :doc:`suffix <suffix>` command in your input script.
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See :doc:`Section_accelerate <Section_accelerate>` of the manual for
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more instructions on how to use the accelerated styles effectively.
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----------
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Restrictions
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""""""""""""
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This angle style can only be used if LAMMPS was built with the
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USER_MISC package. See the :ref:`Making LAMMPS <start_3>`
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section for more info on packages.
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Related commands
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""""""""""""""""
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:doc:`angle_coeff <angle_coeff>`
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**Default:** none
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.. _lws: http://lammps.sandia.gov
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.. _ld: Manual.html
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.. _lc: Section_commands.html#comm
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