"LIGGGHTS(R)-PUBLIC WWW Site"_liws - "LIGGGHTS(R)-PUBLIC Documentation"_ld - "LIGGGHTS(R)-PUBLIC Commands"_lc :c

:link(liws,http://www.cfdem.com)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)

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fix multisphere command :h3

[Syntax:]

fix ID group-ID multisphere :pre

ID, group-ID are documented in "fix"_fix.html command :ulb,l

:ule

[Examples:]

fix ms all multisphere :pre

[Description:]

Treat one or more sets of atoms as independent rigid bodies.  This
means that each timestep the total force and torque on each rigid body
is computed as the sum of the forces and torques on its constituent
particles and the coordinates, velocities, and orientations of the
atoms in each body are updated so that the body moves and rotates as a
single entity. The integration that is performed by this command is
euqivalent to "fix_rigid"_fix_rigid.html. However, the following
implementation details are different:

(1) Body data held by this fix is distributed across all processes, yielding
better parallel scalabilty.

(2) Bodies (particle clumps) can be added/inserted via
"fix_insert_stream"_fix_insert_stream.html,
"fix_insert_rate_region"_fix_insert_rate_region.html or
"fix_insert_pack"_fix_insert_pack.html and are automatically added
to this fix.

(3) A body is removed from the simulation domain if any of it's particles
is removed from the simulation according to the "boundary"_boundary.html
settings or by any command that deleted particles (e.g.
"delete_atoms"_delete_atoms.html).

(4) By using this fix, gravity ("fix_gravity"_fix_gravity.html)
will be handled correctly for for overlapping particle clumps.

(5) This fix internally performs a "neigh_modify"_neigh_modify.html exclude
command so that particles belonging to the same rigid body are excluded
from the neighborlist build.

IMPORTANT NOTE: You should not update the atoms in rigid bodies via
other time-integration fixes (e.g. nve, nvt, npt), or you will be
integrating their motion more than once each timestep.

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[Restart, fix_modify, output, run start/stop, minimize info:]

No information about this fix is written to "binary restart
files"_restart.html.  This means you can currently not restart a simulation
using multisphere particles.

None of the "fix_modify"_fix_modify.html options are relevant to this
fix.  No global scalar or vector or per-atom quantities are stored by
this fix for access by various "output
commands"_Section_howto.html#4_15.  No parameter of this fix can be
used with the {start/stop} keywords of the "run"_run.html command.
This fix is not invoked during "energy minimization"_minimize.html.

[Restrictions:]

Fix multisphere does not work together with "fix deform"_fix_deform.html

Only one fix multisphere at a time is allowed.
Heat transfer simulations are not possible when using this fix
(e.g. "fix heat/gran/conduction"_fix_heat_gran_conduction.html)

The PUBLIC version does not support (i) parallel computation, (ii)
restart of multisphere simulations

IMPORTANT NOTE: All fixes or computes gathering statistical output
(such as e.g. "compute com"_compute_com.html or "fix ave/time"_fix_ave_time.html
operate on a per-sphere rather than on a per-body basis.

Currently, using fix multisphere requires "newton"_newton.html = off and
"dimension"_dimension.html = 3.

[Related commands:]

"fix_rigid"_fix_rigid.html
"fix_particletemplate_sphere"_fix_particletemplate_sphere.html
"neigh_modify"_neigh_modify.html


[Default:] none

