forked from lijiext/lammps
77 lines
2.5 KiB
Plaintext
77 lines
2.5 KiB
Plaintext
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"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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shape command :h3
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[Syntax:]
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mass I x y z :pre
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I = atom type (see asterik form below)
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x = x diameter
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y = y diameter
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z = z diameter :ul
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[Examples:]
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shape 1 1.0 1.0 1.0
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shape * 3.0 1.0 1.0
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shape 2* 3.0 1.0 1.0 :pre
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[Description:]
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Set the shape for all atoms of one or more atom types. Shape values
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can also be set in the "read_data"_read_data.html data file. See the
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"units"_units.html command for what distance units to use.
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Currently, only "atom_style dipole"_atom_style.html and atom_style
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ellipsoid"_atom_style.html require that shapes be set.
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Dipoles use the atom shape to compute a moment of inertia for
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rotational energy. Only the 1st componenet of the shape is used since
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the particles are assumed to be spherical. The value of the first
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component should be the same as the Lennard-Jones sigma value defined
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in the dipole pair potential, i.e. in "pair_style
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dipole"_pair_dipole.html.
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Ellipsoids use the atom shape to compute a generalized inertia tensor.
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For example, a shape setting of 3.0 1.0 1.0 defines a particle 3x
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longer in x than in y or z and with a circular cross-section in yz.
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Ellipsoids that are spherical can be defined by setting all 3 shape
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components the same.
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I can be specified in one of two ways. An explicit numeric value can
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be used, as in the 1st example above. Or a wild-card asterik can be
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used to set the mass for multiple atom types. This takes the form "*"
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or "*n" or "n*" or "m*n". If N = the number of atom types, then an
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asterik with no numeric values means all types from 1 to N. A leading
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asterik means all types from 1 to n (inclusive). A trailing asterik
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means all types from n to N (inclusive). A middle asterik means all
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types from m to n (inclusive).
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A line in a data file that specifies shape uses the same format as the
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arguments of the shape command in an input script, except that no
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wild-card asterik can be used. For example, under the "Shapes"
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section of a data file, the line that corresponds to the 1st example
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above would be listed as
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1 1.0 :pre
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[Restrictions:]
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This command must come after the simulation box is defined by a
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"read_data"_read_data.html, "read_restart"_read_restart.html, or
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"create_box"_create_box.html command.
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All shapes must be defined before a simulation is run (if the atom
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style requires shapes be set).
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[Related commands:] none
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[Default:] none
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