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doc/html/_sources/pair_tri_lj.txt
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doc/html/_sources/pair_tri_lj.txt
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.. index:: pair_style tri/lj
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pair_style tri/lj 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 tri/lj cutoff
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cutoff = global cutoff for interactions (distance units)
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Examples
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""""""""
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.. parsed-literal::
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pair_style tri/lj 3.0
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pair_coeff * * 1.0 1.0
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pair_coeff 1 1 1.0 1.5 2.5
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Description
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"""""""""""
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Style *tri/lj* treats particles which are triangles as a set of small
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spherical particles that tile the triangle surface as explained below.
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Interactions between two triangles, each with N1 and N2 spherical
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particles, are calculated as the pairwise sum of N1*N2 Lennard-Jones
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interactions. Interactions between a triangle with N spherical
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particles and a point particle are treated as the pairwise sum of N
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Lennard-Jones interactions. See the :doc:`pair_style lj/cut <pair_lj>`
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doc page for the definition of Lennard-Jones interactions.
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The cutoff distance for an interaction between 2 triangles, or between
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a triangle and a point particle, is calculated from the position of
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the triangle (its centroid), not between pairs of individual spheres
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comprising the triangle. Thus an interaction is either calculated in
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its entirety or not at all.
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The set of non-overlapping spherical particles that represent a
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triangle, for purposes of this pair style, are generated in the
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following manner. Assume the triangle is of type I, and sigma_II has
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been specified. We want a set of spheres with centers in the plane of
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the triangle, none of them larger in diameter than sigma_II, which
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completely cover the triangle's area, but with minimial overlap and a
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minimal total number of spheres. This is done in a recursive manner.
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Place a sphere at the centroid of the original triangle. Calculate
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what diameter it must have to just cover all 3 corner points of the
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triangle. If that diameter is equal to or smaller than sigma_II, then
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include a sphere of the calculated diameter in the set of covering
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spheres. It the diameter is larger than sigma_II, then split the
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triangle into 2 triangles by bisecting its longest side. Repeat the
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process on each sub-triangle, recursing as far as needed to generate a
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set of covering spheres. When finished, the original criteria are
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met, and the set of covering spheres shoule be near minimal in number
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and overlap, at least for input triangles with a reasonable
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aspect-ratio.
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The LJ interaction between 2 spheres on different triangles of types
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I,J is computed with an arithmetic mixing of the sigma values of the 2
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spheres and using the specified epsilon value for I,J atom types.
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Note that because the sigma values for triangles spheres is computed
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using only sigma_II values, specific to the triangles's type, this
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means that any specified sigma_IJ values (for I != J) are effectively
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ignored.
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For style *tri/lj*\ , the following coefficients must be defined for
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each pair of atoms types via the :doc:`pair_coeff <pair_coeff>` command
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as in the examples above, or in the data file or restart files read by
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the :doc:`read_data <read_data>` or :doc:`read_restart <read_restart>`
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commands:
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* epsilon (energy units)
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* sigma (distance 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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is used.
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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 and sigma coefficients
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and cutoff distance for all of this pair style can be mixed. 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 does not support the :doc:`pair_modify <pair_modify>`
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shift, table, and tail options.
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This pair style does not write its information to :doc:`binary restart files <restart>`.
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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 style is part of the ASPHERE package. It is only enabled if
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LAMMPS was built with that package. See the :ref:`Making LAMMPS <2_3>` section for more info.
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Defining particles to be triangles so they participate in tri/tri or
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tri/particle interactions requires the use the :doc:`atom_style tri <atom_style>` command.
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Related commands
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""""""""""""""""
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:doc:`pair_coeff <pair_coeff>`, :doc:`pair_style line/lj <pair_line_lj>`
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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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