108 lines
3.7 KiB
Plaintext
108 lines
3.7 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 body/rounded/polygon command :h3
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[Syntax:]
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pair_style body/rounded/polygon cutoff_global cutoff_inner delta_ua c_n :pre
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cutoff_global = global cutoff for COM interactions (distance units)
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cutoff_inner = cutoff for vertex-vertex and vertex-edge interactions (distance units)
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delta_ua = characteristic contact length (distance units)
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c_n = normal friction coefficient (energy time/distance^2) :ul
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[Examples:]
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pair_style body/rounded/polygon 6.0 0.5 0.5 0.1
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pair_coeff 1 1 1.0 100.0 12.0 :pre
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[Description:]
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Style {body/rounded/polygon} implements the pairwise body/body
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interactions between 2D convex polygons, as described
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in "Fraige"_#Fraige. This pair style is designed for use with
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the "rounded/polygon" body style, which is specified as
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an argument to the "atom-style body/rounded/polygon" command.
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See the "body"_body.html doc page for more details about the body
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styles LAMMPS supports.
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The "rounded/polygon" style treats a body particle as a discrete
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element model (DEM) polygon composed of N vertices.
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The coordinates of a body particle are its center-of-mass (COM).
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The initial position of the vertices are specified the data file.
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The current implementation follows the multiple contact points model as
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described in "Fraige"_#Fraige, but neglects and the contact history
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the tangential contact forces for now.
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The parameters {delta_ua} and {c_n} are the characteristic contact length
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and the normal friction coefficient, respectively. See Eqs. (1) and (5)
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in "Fraige"_#Fraige for more details.
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For style {body/rounded/polygon}, the following coefficients
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must be defined for each pair of atoms types via the "pair_coeff"_pair_coeff.html
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command as in the examples above:
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sigma = vertex rounded diameter (distance units)
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k_n = normal repulsion strength (energy/distance^2)
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k_na = normal attraction strength (energy/distance^2)
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cutoff = cutoff for COM interactions (distance units) :ul
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The last parameter is optional. If not specified, the global
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cutoff specified in the pair_style command is used.
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Note that the current implementation assumes that the edge length
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of the polygons (L) should be at least twice greater than
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the vertex rounded radius (sigma) so as to distinguish vertex-vertex from
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vertex-edge contacts.
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NOTE: Because this pair style requires the body velocities to compute
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the friction component of the forces, users should specify
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{comm_modify vel yes} in the input script with this pair style.
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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 BODY package. It is only enabled if LAMMPS
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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 bodies so they participate in body/body or
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body/particle interactions requires the use of the "atom_style
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body"_atom_style.html command.
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[Related commands:]
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"pair_coeff"_pair_coeff.html
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[Default:] none
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:link(Fraige)
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[(Fraige)] F. Y. Fraige, P. A. Langston, A. J. Matchett, J. Dodds,
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Particuology, 6, 455 (2008).
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