forked from lijiext/lammps
139 lines
5.4 KiB
Plaintext
139 lines
5.4 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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pair_style tri/lj command :h3
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pair_style tri/lj/omp command :h3
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[Syntax:]
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pair_style tri/lj cutoff :pre
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cutoff = global cutoff for interactions (distance units)
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[Examples:]
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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 :pre
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[Description:]
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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 "pair_style lj/cut"_pair_lj.html
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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 "pair_coeff"_pair_coeff.html 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 "read_data"_read_data.html or "read_restart"_read_restart.html
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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) :ul
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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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:line
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Styles with a {cuda}, {gpu}, {omp}, or {opt} suffix are functionally
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the same as the corresponding style without the suffix. They have
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been optimized to run faster, depending on your available hardware, as
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discussed in "Section_accelerate"_Section_accelerate.html of the
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manual. The accelerated styles take the same arguments and should
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produce the same results, except for round-off and precision issues.
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These accelerated styles are part of the USER-CUDA, GPU, USER-OMP and OPT
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packages, respectively. They are only enabled if LAMMPS was built with
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those packages. See the "Making LAMMPS"_Section_start.html#start_3
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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 "-suffix command-line
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switch"_Section_start.html#start_7 when you invoke LAMMPS, or you can
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use the "suffix"_suffix.html command in your input script.
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See "Section_accelerate"_Section_accelerate.html of the manual for
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more instructions on how to use the accelerated styles effectively.
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:line
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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 "pair_modify"_pair_modify.html
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shift, table, and tail options.
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This pair style does not write its information to "binary restart
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files"_restart.html.
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This pair style can only be used via the {pair} keyword of the
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"run_style respa"_run_style.html command. It does not support the
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{inner}, {middle}, {outer} keywords.
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:line
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[Restrictions:]
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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 "Making
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LAMMPS"_Section_start.html#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 "atom_style
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tri"_atom_style.html command.
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[Related commands:]
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"pair_coeff"_pair_coeff.html, "pair_style line/lj"_pair_line_lj.html
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[Default:] none
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