forked from lijiext/lammps
104 lines
3.1 KiB
Plaintext
104 lines
3.1 KiB
Plaintext
.. index:: pair_style born/coul/long/cs
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pair_style born/coul/long/cs command
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====================================
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pair_style buck/coul/long/cs command
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====================================
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Syntax
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""""""
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.. parsed-literal::
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pair_style style args
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* style = *born/coul/long/cs* or *buck/coul/long/cs*
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* args = list of arguments for a particular style
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.. parsed-literal::
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*born/coul/long/cs* args = cutoff (cutoff2)
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cutoff = global cutoff for non-Coulombic (and Coulombic if only 1 arg) (distance units)
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cutoff2 = global cutoff for Coulombic (optional) (distance units)
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*buck/coul/long/cs* args = cutoff (cutoff2)
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cutoff = global cutoff for Buckingham (and Coulombic if only 1 arg) (distance units)
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cutoff2 = global cutoff for Coulombic (optional) (distance units)
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Examples
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""""""""
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.. parsed-literal::
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pair_style born/coul/long/cs 10.0 8.0
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pair_coeff 1 1 6.08 0.317 2.340 24.18 11.51
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.. parsed-literal::
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pair_style buck/coul/long/cs 10.0
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pair_style buck/coul/long/cs 10.0 8.0
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pair_coeff * * 100.0 1.5 200.0
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pair_coeff 1 1 100.0 1.5 200.0 9.0
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Description
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"""""""""""
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These pair styles are designed to be used with the adiabatic
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core/shell model of :ref:`(Mitchell and Finchham) <MitchellFinchham>`. See
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:ref:`Section_howto 25 <howto_25>` of the manual for an
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overview of the model as implemented in LAMMPS.
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These pair styles are identical to the :doc:`pair_style born/coul/long <pair_born>` and :doc:`pair_style buck/coul/long <pair_buck>` styles, except they correctly treat the
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special case where the distance between two charged core and shell
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atoms in the same core/shell pair approach r = 0.0. This needs
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special treatment when a long-range solver for Coulombic interactions
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is also used, i.e. via the :doc:`kspace_style <kspace_style>` command.
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More specifically, the short-range Coulomb interaction between a core
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and its shell should be turned off using the
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:doc:`special_bonds <special_bonds>` command by setting the 1-2 weight
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to 0.0, which works because the core and shell atoms are bonded to
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each other. This induces a long-range correction approximation which
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fails at small distances (~< 10e-8). Therefore, the Coulomb term which
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is used to calculate the correction factor is extended by a minimal
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distance (r_min = 1.0-6) when the interaction between a core/shell
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pair is treated, as follows
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.. image:: Eqs/pair_cs.jpg
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:align: center
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where C is an energy-conversion constant, Qi and Qj are the charges on
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the core and shell, epsilon is the dielectric constant and r_min is the
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minimal distance.
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Restrictions
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""""""""""""
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These pair styles are part of the CORESHELL 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.
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Related commands
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""""""""""""""""
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:doc:`pair_coeff <pair_coeff>`, :doc:`pair_style born <pair_born>`,
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:doc:`pair_style buck <pair_buck>`
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**Default:** none
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----------
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.. _MitchellFinchham:
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**(Mitchell and Finchham)** Mitchell, Finchham, J Phys Condensed Matter,
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5, 1031-1038 (1993).
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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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