129 lines
3.7 KiB
ReStructuredText
129 lines
3.7 KiB
ReStructuredText
.. index:: pair_style lj/expand
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.. index:: pair_style lj/expand/gpu
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.. index:: pair_style lj/expand/kk
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.. index:: pair_style lj/expand/omp
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.. index:: pair_style lj/expand/coul/long
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.. index:: pair_style lj/expand/coul/long/kk
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.. index:: pair_style lj/expand/coul/long/gpu
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pair_style lj/expand command
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============================
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Accelerator Variants: *lj/expand/gpu*, *lj/expand/kk*, *lj/expand/omp*
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pair_style lj/expand/coul/long command
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======================================
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Accelerator Variants: *lj/expand/coul/long/gpu*, *lj/expand/coul/long/kk*
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Syntax
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""""""
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.. code-block:: LAMMPS
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pair_style lj/expand cutoff
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* cutoff = global cutoff for lj/expand 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 lj/expand 2.5
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pair_coeff * * 1.0 1.0 0.5
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pair_coeff 1 1 1.0 1.0 -0.2 2.0
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pair_style lj/expand/coul/long 2.5
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pair_style lj/expand/coul/long 2.5 4.0
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pair_coeff * * 1.0 1.0 0.5
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pair_coeff 1 1 1.0 1.0 -0.2 3.0
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Description
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"""""""""""
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Style *lj/expand* computes a LJ interaction with a distance shifted by
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delta which can be useful when particles are of different sizes, since
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it is different that using different sigma values in a standard LJ
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formula:
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.. math::
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E = 4 \epsilon \left[ \left(\frac{\sigma}{r - \Delta}\right)^{12} -
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\left(\frac{\sigma}{r - \Delta}\right)^6 \right]
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\qquad r < r_c + \Delta
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:math:`r_c` is the cutoff which does not include the :math:`\Delta`
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distance. I.e. the actual force cutoff is the sum of :math:`r_c +
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\Delta`.
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For all of the *lj/expand* pair styles, the following coefficients must
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be defined for each pair of atoms types via the :doc:`pair_coeff
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<pair_coeff>` command as in the examples above, or in the data file or
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restart files read by the :doc:`read_data <read_data>` or
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:doc:`read_restart <read_restart>` commands, or by mixing as described
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below:
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* :math:`\epsilon` (energy units)
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* :math:`\sigma` (distance units)
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* :math:`\Delta` (distance units)
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* cutoff (distance units)
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The :math:`\Delta` values can be positive or negative. The last
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coefficient is optional. If not specified, the global LJ cutoff is
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used.
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For *lj/expand/coul/long* only the LJ cutoff can be specified since a
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Coulombic cutoff cannot be specified for an individual I,J type pair.
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All type pairs use the same global Coulombic cutoff specified in the
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pair_style command.
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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, the epsilon, sigma, and shift
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coefficients and cutoff distance for this pair style can be mixed.
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Shift is always mixed via an *arithmetic* rule. The other
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coefficients are mixed according to the pair_modify mix value. The
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default mix value is *geometric*\ . See the "pair_modify" command for
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details.
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This pair style supports 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 supports the :doc:`pair_modify <pair_modify>` tail
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option for adding a long-range tail correction to the energy and
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pressure of the pair interaction.
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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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none
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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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