forked from lijiext/lammps
124 lines
5.0 KiB
Plaintext
124 lines
5.0 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
|
|
|
|
:link(lws,http://lammps.sandia.gov)
|
|
:link(ld,Manual.html)
|
|
:link(lc,Section_commands.html#comm)
|
|
|
|
:line
|
|
|
|
atom_style command :h3
|
|
|
|
[Syntax:]
|
|
|
|
atom_style style args :pre
|
|
|
|
style = {angle} or {atomic} or {bond} or {charge} or {dipole} or \
|
|
{dpd} or {ellipsoid} or {full} or {granular} or {molecular} or \
|
|
{peri} or {hybrid} :ul
|
|
args = none for any style except {hybrid}
|
|
{hybrid} args = list of one or more sub-styles :pre
|
|
|
|
[Examples:]
|
|
|
|
atom_style atomic
|
|
atom_style bond
|
|
atom_style full
|
|
atom_style hybrid charge bond :pre
|
|
|
|
[Description:]
|
|
|
|
Define what style of atoms to use in a simulation. This determines
|
|
what attributes are associated with the atoms. This command must be
|
|
used before a simulation is setup via a "read_data"_read_data.html,
|
|
"read_restart"_read_restart.html, or "create_box"_create_box.html
|
|
command.
|
|
|
|
Once a style is assigned, it cannot be changed, so use a style general
|
|
enough to encompass all attributes. E.g. with style {bond}, angular
|
|
terms cannot be used or added later to the model. It is OK to use a
|
|
style more general than needed, though it may be slightly inefficient.
|
|
|
|
The choice of style affects what quantities are stored by each atom,
|
|
what quantities are communicated between processors to enable forces
|
|
to be computed, and what quantities are listed in the data file read
|
|
by the "read_data"_read_data.html command.
|
|
|
|
These are the additional attributes of each style and the typical
|
|
kinds of physical systems they are used to model. All styles store
|
|
coordinates, velocities, atom IDs and types. See the
|
|
"read_data"_read_data.html, "create_atoms"_create_atoms.html, and
|
|
"set"_set.html commands for info on how to set these various
|
|
quantities.
|
|
|
|
{angle} | bonds and angles | bead-spring polymers with stiffness |
|
|
{atomic} | only the default values | coarse-grain liquids, solids, metals |
|
|
{bond} | bonds | bead-spring polymers |
|
|
{charge} | charge | atomic system with charges |
|
|
{dipole} | charge and dipole moment | atomic system with dipoles |
|
|
{dpd} | default values, also communicates velocities | DPD models |
|
|
{ellipsoid} | quaternion for particle orientation, angular momentum | aspherical particles |
|
|
{full} | molecular + charge | bio-molecules |
|
|
{granular} | diameter, density, angular velocity | granular models |
|
|
{molecular} | bonds, angles, dihedrals, impropers | uncharged molecules |
|
|
{peri} | density, volume | mesocopic Peridynamic models :tb(c=3,s=|)
|
|
|
|
All of the styles define point particles, except the {ellipsoid} and
|
|
{granular} and {peri} styles. These define finite-size particles.
|
|
For {ellipsoidal} systems, the "shape"_shape.html command is used to
|
|
specify the size and shape of particles, which can be spherical or
|
|
aspherical. For {granular} systems, the particles are spherical and
|
|
each has a specified diameter. For {peri} systems, the particles are
|
|
spherical and each has a specified volume.
|
|
|
|
All of the styles assign mass to particles on a per-type basis, using
|
|
the "mass"_mass.html command, except the {granular} and {peri} styles.
|
|
For {granular} systems, the specified diameter and density are used to
|
|
calculate each particle's mass. For {peri} systems, the speficied
|
|
volume and density are used to calculate each particle's mass.
|
|
|
|
Only the {dpd} and {granular} styles communicate velocities with ghost
|
|
atoms; the others do not. This is because the pairwise interactions
|
|
calculated by the "pair_style dpd"_pair_dpd.html and "pair_style
|
|
granular"_pair_gran.html commands require velocities.
|
|
|
|
:line
|
|
|
|
Typically, simulations require only a single (non-hybrid) atom style.
|
|
If some atoms in the simulation do not have all the properties defined
|
|
by a particular style, use the simplest style that defines all the
|
|
needed properties by any atom. For example, if some atoms in a
|
|
simulation are charged, but others are not, use the {charge} style.
|
|
If some atoms have bonds, but others do not, use the {bond} style.
|
|
|
|
The only scenario where the {hybrid} style is needed is if there is no
|
|
single style which defines all needed properties of all atoms. For
|
|
example, if you want charged DPD particles, you would need to use
|
|
"atom_style hybrid dpd charge". When a hybrid style is used, atoms
|
|
store and communicate the union of all quantities implied by the
|
|
individual styles.
|
|
|
|
LAMMPS can be extended with new atom styles; see "this
|
|
section"_Section_modify.html.
|
|
|
|
[Restrictions:]
|
|
|
|
This command cannot be used after the simulation box is defined by a
|
|
"read_data"_read_data.html or "create_box"_create_box.html command.
|
|
|
|
The {angle}, {bond}, {full}, and {molecular} styles are part of the
|
|
"molecular" package. The {granular} style is part of the "granular"
|
|
package. The {dpd} style is part of the "dpd" package. The {dipole}
|
|
style is part of the "dipole" package. The {ellipsoid} style is part
|
|
of the "asphere" package. The {peri} style is part of the "peri"
|
|
package for Peridynamics. They are only enabled if LAMMPS was built
|
|
with that package. See the "Making LAMMPS"_Section_start.html#2_3
|
|
section for more info.
|
|
|
|
[Related commands:]
|
|
|
|
"read_data"_read_data.html, "pair_style"_pair_style.html
|
|
|
|
[Default:]
|
|
|
|
atom_style atomic
|