71 lines
1.4 KiB
ReStructuredText
71 lines
1.4 KiB
ReStructuredText
.. index:: dihedral_style quadratic
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.. index:: dihedral_style quadratic/omp
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dihedral_style quadratic command
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================================
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Accelerator Variants: *quadratic/omp*
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Syntax
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""""""
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.. code-block:: LAMMPS
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dihedral_style quadratic
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Examples
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""""""""
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.. code-block:: LAMMPS
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dihedral_style quadratic
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dihedral_coeff 100.0 80.0
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Description
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"""""""""""
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The *quadratic* dihedral style uses the potential:
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.. math::
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E = K (\phi - \phi_0)^2
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This dihedral potential can be used to keep a dihedral in a predefined
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value (cis=zero, right-hand convention is used).
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The following coefficients must be defined for each dihedral type via
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the :doc:`dihedral_coeff <dihedral_coeff>` command as in the example
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above, or in the data file or restart files read by the
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:doc:`read_data <read_data>` or :doc:`read_restart <read_restart>`
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commands:
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* :math:`K` (energy)
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* :math:`\phi_0` (degrees)
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:math:`\phi_0` is specified in degrees, but LAMMPS converts it to
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radians internally; hence :math:`K` is effectively energy per
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radian\^2.
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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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EXTRA-MOLECULE package. See the :doc:`Build package <Build_package>` doc
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page 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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