forked from lijiext/lammps
130 lines
3.8 KiB
Plaintext
130 lines
3.8 KiB
Plaintext
.. index:: pair_style lj/expand
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pair_style lj/expand command
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============================
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pair_style lj/expand/gpu command
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================================
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pair_style lj/expand/omp 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 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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.. parsed-literal::
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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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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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.. image:: Eqs/pair_lj_expand.jpg
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:align: center
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Rc is the cutoff which does not include the delta distance. I.e. the
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actual force cutoff is the sum of cutoff + delta.
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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, or by mixing as described below:
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* epsilon (energy units)
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* sigma (distance units)
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* delta (distance units)
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* cutoff (distance units)
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The delta values can be positive or negative. The last coefficient is
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optional. If not specified, the global LJ cutoff is used.
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----------
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Styles with a *gpu*\ , *intel*\ , *kk*\ , *omp*\ , or *opt* suffix are
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functionally the same as the corresponding style without the suffix.
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They have been optimized to run faster, depending on your available
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hardware, as discussed in :doc:`Section_accelerate <Section_accelerate>`
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of the manual. The accelerated styles take the same arguments and
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should produce the same results, except for round-off and precision
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issues.
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These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,
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USER-OMP and OPT packages, respectively. They are only enabled if
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LAMMPS was built with those packages. See the :ref:`Making LAMMPS <start_3>` section for more info.
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You can specify the accelerated styles explicitly in your input script
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by including their suffix, or you can use the :ref:`-suffix command-line switch <start_7>` when you invoke LAMMPS, or you can
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use the :doc:`suffix <suffix>` command in your input script.
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See :doc:`Section_accelerate <Section_accelerate>` of the manual for
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more instructions on how to use the accelerated styles effectively.
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----------
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**Mixing, shift, table, tail correction, restart, rRESPA info**\ :
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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:** none
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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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