79 lines
1.8 KiB
ReStructuredText
79 lines
1.8 KiB
ReStructuredText
.. index:: dihedral_style harmonic
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.. index:: dihedral_style harmonic/intel
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.. index:: dihedral_style harmonic/kk
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.. index:: dihedral_style harmonic/omp
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dihedral_style harmonic command
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===============================
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Accelerator Variants: *harmonic/intel*, *harmonic/kk*, *harmonic/omp*
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Syntax
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""""""
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.. code-block:: LAMMPS
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dihedral_style harmonic
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Examples
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""""""""
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.. code-block:: LAMMPS
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dihedral_style harmonic
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dihedral_coeff 1 80.0 1 2
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Description
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"""""""""""
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The *harmonic* dihedral style uses the potential
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.. math::
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E = K [ 1 + d \cos (n \phi) ]
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The following coefficients must be defined for each dihedral type via the
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:doc:`dihedral_coeff <dihedral_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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* :math:`K` (energy)
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* :math:`d` (+1 or -1)
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* :math:`n` (integer >= 0)
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.. note::
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Here are important points to take note of when defining LAMMPS
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dihedral coefficients for the harmonic style, so that they are
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compatible with how harmonic dihedrals are defined by other force
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fields:
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* The LAMMPS convention is that the trans position = 180 degrees, while
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in some force fields trans = 0 degrees.
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* Some force fields reverse the sign convention on :math:`d`.
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* Some force fields let :math:`n` be positive or negative which corresponds to
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:math:`d = 1` or :math:`d = -1` for the harmonic style.
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----------
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.. include:: accel_styles.rst
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----------
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Restrictions
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""""""""""""
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This dihedral style can only be used if LAMMPS was built with the
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MOLECULE package. See the :doc:`Build package <Build_package>` doc page
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for more info.
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Related commands
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""""""""""""""""
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:doc:`dihedral_coeff <dihedral_coeff>`
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Default
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"""""""
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none
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