107 lines
2.7 KiB
ReStructuredText
107 lines
2.7 KiB
ReStructuredText
.. index:: pair_style beck
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.. index:: pair_style beck/gpu
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.. index:: pair_style beck/omp
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pair_style beck command
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=======================
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Accelerator Variants: *beck/gpu*, *beck/omp*
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Syntax
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""""""
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.. code-block:: LAMMPS
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pair_style beck Rc
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* Rc = cutoff for interactions (distance units)
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Examples
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""""""""
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.. code-block:: LAMMPS
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pair_style beck 8.0
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pair_coeff * * 399.671876712 0.0000867636112694 0.675 4.390 0.0003746
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pair_coeff 1 1 399.671876712 0.0000867636112694 0.675 4.390 0.0003746 6.0
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Description
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"""""""""""
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Style *beck* computes interactions based on the potential by
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:ref:`(Beck) <Beck>`, originally designed for simulation of Helium. It
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includes truncation at a cutoff distance :math:`r_c`.
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.. math::
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E(r) &= A \exp\left[-\alpha r - \beta r^6\right] - \frac{B}{\left(r^2+a^2\right)^3} \left(1+\frac{2.709+3a^2}{r^2+a^2}\right) \qquad r < r_c \\
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The following coefficients must be defined for each pair of atoms
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types via the :doc:`pair_coeff <pair_coeff>` command as in the examples
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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:`A` (energy units)
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* :math:`B` (energy-distance\^6 units)
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* :math:`a` (distance units)
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* :math:`\alpha` (1/distance units)
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* :math:`\beta` (1/distance\^6 units)
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* cutoff (distance units)
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The last coefficient is optional. If not specified, the global cutoff
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:math:`r_c` is used.
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----------
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.. include:: accel_styles.rst
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----------
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Mixing, shift, table, tail correction, restart, rRESPA info
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"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
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For atom type pairs I,J and I != J, coefficients must be specified.
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No default mixing rules are used.
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This pair style does not support the :doc:`pair_modify <pair_modify>` shift
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option for the energy of the pair interaction.
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The :doc:`pair_modify <pair_modify>` table option is not relevant
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for this pair style.
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This pair style does not support the :doc:`pair_modify <pair_modify>`
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tail option for adding long-range tail corrections.
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This pair style writes its information to :doc:`binary restart files <restart>`, so pair_style and pair_coeff commands do not need
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to be specified in an input script that reads a restart file.
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This pair style can only be used via the *pair* keyword of the
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:doc:`run_style respa <run_style>` command. It does not support the
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*inner*, *middle*, *outer* keywords.
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----------
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Restrictions
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""""""""""""
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This pair style is part of the EXTRA-PAIR package. It is only enabled if
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LAMMPS was built with that package. See the
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:doc:`Build package <Build_package>` page for more info.
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Related commands
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""""""""""""""""
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:doc:`pair_coeff <pair_coeff>`
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Default
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"""""""
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none
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----------
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.. _Beck:
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**(Beck)** Beck, Molecular Physics, 14, 311 (1968).
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