66 lines
1.5 KiB
ReStructuredText
66 lines
1.5 KiB
ReStructuredText
.. index:: improper_style distance
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improper_style distance command
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===============================
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Syntax
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""""""
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.. code-block:: LAMMPS
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improper_style distance
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Examples
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""""""""
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.. code-block:: LAMMPS
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improper_style distance
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improper_coeff 1 80.0 100.0
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Description
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"""""""""""
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The *distance* improper style uses the potential
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.. math::
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E = K_2 d^2 + K_4 d^4
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where :math:`d` is the distance between the central atom and the plane formed
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by the other three atoms. If the 4 atoms in an improper quadruplet
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(listed in the data file read by the :doc:`read_data <read_data>`
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command) are ordered I,J,K,L then the I-atom is assumed to be the
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central atom.
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.. image:: JPG/improper_distance.jpg
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:align: center
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Note that defining 4 atoms to interact in this way, does not mean that
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bonds necessarily exist between I-J, J-K, or K-L, as they would in a
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linear dihedral. Normally, the bonds I-J, I-K, I-L would exist for an
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improper to be defined between the 4 atoms.
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The following coefficients must be defined for each improper type via
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the improper_coeff command as in the example above, or in the data
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file or restart files read by the read_data or read_restart commands:
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* :math:`K_2` (energy/distance\^2)
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* :math:`K_4` (energy/distance\^4)
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----------
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Restrictions
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""""""""""""
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This improper style can only be used if LAMMPS was built with the
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USER-MISC 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:`improper_coeff <improper_coeff>`
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**Default:** none
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