forked from lijiext/lammps
114 lines
3.5 KiB
Plaintext
114 lines
3.5 KiB
Plaintext
.. index:: angle_style
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angle_style 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 style
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* style = *none* or *hybrid* or *charmm* or *class2* or *cosine* or *cosine/squared* or *harmonic*
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Examples
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""""""""
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.. parsed-literal::
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angle_style harmonic
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angle_style charmm
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angle_style hybrid harmonic cosine
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Description
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"""""""""""
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Set the formula(s) LAMMPS uses to compute angle interactions between
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triplets of atoms, which remain in force for the duration of the
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simulation. The list of angle triplets is read in by a
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:doc:`read_data <read_data>` or :doc:`read_restart <read_restart>` command
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from a data or restart file.
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Hybrid models where angles are computed using different angle
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potentials can be setup using the *hybrid* angle style.
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The coefficients associated with a angle style can be specified in a
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data or restart file or via the :doc:`angle_coeff <angle_coeff>` command.
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All angle potentials store their coefficient data in binary restart
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files which means angle_style and :doc:`angle_coeff <angle_coeff>`
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commands do not need to be re-specified in an input script that
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restarts a simulation. See the :doc:`read_restart <read_restart>`
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command for details on how to do this. The one exception is that
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angle_style *hybrid* only stores the list of sub-styles in the restart
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file; angle coefficients need to be re-specified.
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.. note::
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When both an angle and pair style is defined, the
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:doc:`special_bonds <special_bonds>` command often needs to be used to
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turn off (or weight) the pairwise interaction that would otherwise
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exist between 3 bonded atoms.
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In the formulas listed for each angle style, *theta* is the angle
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between the 3 atoms in the angle.
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----------
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Here is an alphabetic list of angle styles defined in LAMMPS. Click on
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the style to display the formula it computes and coefficients
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specified by the associated :doc:`angle_coeff <angle_coeff>` command.
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Note that there are also additional angle styles submitted by users
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which are included in the LAMMPS distribution. The list of these with
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links to the individual styles are given in the angle section of :ref:`this page <cmd_5>`.
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* :doc:`angle_style none <angle_none>` - turn off angle interactions
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* :doc:`angle_style zero <angle_zero>` - topology but no interactions
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* :doc:`angle_style hybrid <angle_hybrid>` - define multiple styles of angle interactions
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* :doc:`angle_style charmm <angle_charmm>` - CHARMM angle
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* :doc:`angle_style class2 <angle_class2>` - COMPASS (class 2) angle
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* :doc:`angle_style cosine <angle_cosine>` - cosine angle potential
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* :doc:`angle_style cosine/delta <angle_cosine_delta>` - difference of cosines angle potential
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* :doc:`angle_style cosine/periodic <angle_cosine_periodic>` - DREIDING angle
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* :doc:`angle_style cosine/squared <angle_cosine_squared>` - cosine squared angle potential
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* :doc:`angle_style harmonic <angle_harmonic>` - harmonic angle
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* :doc:`angle_style table <angle_table>` - tabulated by angle
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----------
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Restrictions
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""""""""""""
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Angle styles can only be set for atom_styles that allow angles to be
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defined.
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Most angle styles are part of the MOLECULE package. They are only
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enabled if LAMMPS was built with that package. See the :ref:`Making LAMMPS <start_3>` section for more info on packages.
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The doc pages for individual bond potentials tell if it is part of a
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package.
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Related commands
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""""""""""""""""
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:doc:`angle_coeff <angle_coeff>`
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Default
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"""""""
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.. parsed-literal::
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angle_style 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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