86 lines
1.8 KiB
ReStructuredText
86 lines
1.8 KiB
ReStructuredText
.. index:: angle_style charmm
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.. index:: angle_style charmm/intel
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.. index:: angle_style charmm/kk
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.. index:: angle_style charmm/omp
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angle_style charmm command
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==========================
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Accelerator Variants: *charmm/intel*, *charmm/kk*, *charmm/omp*
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Syntax
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""""""
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.. code-block:: LAMMPS
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angle_style charmm
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Examples
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""""""""
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.. code-block:: LAMMPS
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angle_style charmm
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angle_coeff 1 300.0 107.0 50.0 3.0
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Description
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"""""""""""
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The *charmm* angle style uses the potential
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.. math::
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E = K (\theta - \theta_0)^2 + K_{ub} (r - r_{ub})^2
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with an additional Urey_Bradley term based on the distance :math:`r` between
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the first and third atoms in the angle. :math:`K`, :math:`\theta_0`,
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:math:`K_{ub}`, and :math:`R_{ub}` are coefficients defined for each angle
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type.
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See :ref:`(MacKerell) <angle-MacKerell>` for a description of the CHARMM force
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field.
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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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* :math:`K` (energy)
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* :math:`\theta_0` (degrees)
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* :math:`K_{ub}` (energy/distance\^2)
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* :math:`r_{ub}` (distance)
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:math:`\theta_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 angle 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:`angle_coeff <angle_coeff>`
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Default
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"""""""
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none
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----------
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.. _angle-MacKerell:
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**(MacKerell)** MacKerell, Bashford, Bellott, Dunbrack, Evanseck, Field,
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Fischer, Gao, Guo, Ha, et al, J Phys Chem, 102, 3586 (1998).
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