forked from lijiext/lammps
123 lines
5.0 KiB
Plaintext
123 lines
5.0 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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atom_style command :h3
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[Syntax:]
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atom_style style args :pre
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style = {angle} or {atomic} or {bond} or {charge} or {colloid} or {dipole} or \
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{ellipsoid} or {full} or {granular} or {molecular} or \
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{peri} or {hybrid} :ul
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args = none for any style except {hybrid}
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{hybrid} args = list of one or more sub-styles :pre
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[Examples:]
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atom_style atomic
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atom_style bond
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atom_style full
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atom_style hybrid charge bond :pre
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[Description:]
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Define what style of atoms to use in a simulation. This determines
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what attributes are associated with the atoms. This command must be
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used before a simulation is setup via a "read_data"_read_data.html,
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"read_restart"_read_restart.html, or "create_box"_create_box.html
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command.
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Once a style is assigned, it cannot be changed, so use a style general
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enough to encompass all attributes. E.g. with style {bond}, angular
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terms cannot be used or added later to the model. It is OK to use a
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style more general than needed, though it may be slightly inefficient.
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The choice of style affects what quantities are stored by each atom,
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what quantities are communicated between processors to enable forces
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to be computed, and what quantities are listed in the data file read
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by the "read_data"_read_data.html command.
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These are the additional attributes of each style and the typical
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kinds of physical systems they are used to model. All styles store
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coordinates, velocities, atom IDs and types. See the
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"read_data"_read_data.html, "create_atoms"_create_atoms.html, and
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"set"_set.html commands for info on how to set these various
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quantities.
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{angle} | bonds and angles | bead-spring polymers with stiffness |
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{atomic} | only the default values | coarse-grain liquids, solids, metals |
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{bond} | bonds | bead-spring polymers |
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{charge} | charge | atomic system with charges |
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{colloid} | angular velocity | extended spherical particles |
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{dipole} | charge and dipole moment | atomic system with dipoles |
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{ellipsoid} | quaternion for particle orientation, angular momentum | extended aspherical particles |
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{full} | molecular + charge | bio-molecules |
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{granular} | diameter, density, angular velocity | granular models |
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{molecular} | bonds, angles, dihedrals, impropers | uncharged molecules |
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{peri} | density, volume | mesocopic Peridynamic models :tb(c=3,s=|)
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All of the styles define point particles, except the {colloid},
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{dipole}, {ellipsoid}, {granular}, and {peri} styles, which define
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finite-size particles. For {colloid}, {dipole}, and {ellipsoid}
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systems, the "shape"_shape.html command is used to specify the size
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and shape of particles on a per-type basis, which is spherical for
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{colloid} and {dipole} particles and spherical or aspherical for
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{ellipsoid} particles. For {granular} systems, the particles are
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spherical and each has a per-particle specified diameter. For {peri}
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systems, the particles are spherical and each has a per-particle
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specified volume.
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All of the styles assign mass to particles on a per-type basis, using
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the "mass"_mass.html command, except the {granular} and {peri} styles
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which assign mass on a per-particle basis. For {granular} systems,
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the specified diameter and density are used to calculate each
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particle's mass. For {peri} systems, the speficied volume and density
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are used to calculate each particle's mass.
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:line
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Typically, simulations require only a single (non-hybrid) atom style.
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If some atoms in the simulation do not have all the properties defined
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by a particular style, use the simplest style that defines all the
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needed properties by any atom. For example, if some atoms in a
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simulation are charged, but others are not, use the {charge} style.
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If some atoms have bonds, but others do not, use the {bond} style.
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The only scenario where the {hybrid} style is needed is if there is no
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single style which defines all needed properties of all atoms. For
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example, if you want colloidal particles with charge, you would need
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to use "atom_style hybrid colloid charge". When a hybrid style is
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used, atoms store and communicate the union of all quantities implied
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by the individual styles.
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LAMMPS can be extended with new atom styles; see "this
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section"_Section_modify.html.
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[Restrictions:]
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This command cannot be used after the simulation box is defined by a
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"read_data"_read_data.html or "create_box"_create_box.html command.
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The {angle}, {bond}, {full}, and {molecular} styles are part of the
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"molecular" package. The {granular} style is part of the "granular"
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package. The {colloid} style is part of the "colloid" package. The
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{dipole} style is part of the "dipole" package. The {ellipsoid} style
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is part of the "asphere" package. The {peri} style is part of the
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"peri" package for Peridynamics. They are only enabled if LAMMPS was
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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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[Related commands:]
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"read_data"_read_data.html, "pair_style"_pair_style.html
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[Default:]
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atom_style atomic
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