"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Commands_all.html)

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fix nve/sphere command :h3
fix nve/sphere/omp command :h3
fix nve/sphere/kk command :h3

[Syntax:]

fix ID group-ID nve/sphere :pre

ID, group-ID are documented in "fix"_fix.html command :ulb,l
nve/sphere = style name of this fix command :l
zero or more keyword/value pairs may be appended :l
keyword = {update} or {disc} :l
  {update} value = {dipole} or {dipole/dlm}
    dipole = update orientation of dipole moment during integration
    dipole/dlm = use DLM integrator to update dipole orientation
  {disc} value = none = treat particles as 2d discs, not spheres :pre
:ule

[Examples:]

fix 1 all nve/sphere
fix 1 all nve/sphere update dipole
fix 1 all nve/sphere disc
fix 1 all nve/sphere update dipole/dlm :pre

[Description:]

Perform constant NVE integration to update position, velocity, and
angular velocity for finite-size spherical particles in the group each
timestep.  V is volume; E is energy.  This creates a system trajectory
consistent with the microcanonical ensemble.

This fix differs from the "fix nve"_fix_nve.html command, which
assumes point particles and only updates their position and velocity.

If the {update} keyword is used with the {dipole} value, then the
orientation of the dipole moment of each particle is also updated
during the time integration.  This option should be used for models
where a dipole moment is assigned to finite-size particles,
e.g. spheroids via use of the "atom_style hybrid sphere
dipole"_atom_style.html command.

The default dipole orientation integrator can be changed to the
Dullweber-Leimkuhler-McLachlan integration scheme
"(Dullweber)"_#nh-Dullweber when using {update} with the value
{dipole/dlm}. This integrator is symplectic and time-reversible,
giving better energy conservation and allows slightly longer timesteps
at only a small additional computational cost.

If the {disc} keyword is used, then each particle is treated as a 2d
disc (circle) instead of as a sphere.  This is only possible for 2d
simulations, as defined by the "dimension"_dimension.html keyword.
The only difference between discs and spheres in this context is their
moment of inertia, as used in the time integration.

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Styles with a {gpu}, {intel}, {kk}, {omp}, or {opt} suffix are
functionally the same as the corresponding style without the suffix.
They have been optimized to run faster, depending on your available
hardware, as discussed on the "Speed packages"_Speed_packages.html doc
page.  The accelerated styles take the same arguments and should
produce the same results, except for round-off and precision issues.

These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,
USER-OMP and OPT packages, respectively.  They are only enabled if
LAMMPS was built with those packages.  See the "Build
package"_Build_package.html doc page for more info.

You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the "-suffix command-line
switch"_Run_options.html when you invoke LAMMPS, or you can use the
"suffix"_suffix.html command in your input script.

See the "Speed packages"_Speed_packages.html doc page for more
instructions on how to use the accelerated styles effectively.

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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.  None of the "fix_modify"_fix_modify.html options
are relevant to this fix.  No global or per-atom quantities are stored
by this fix for access by various "output commands"_Howto_output.html.
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:]

This fix requires that atoms store torque and angular velocity (omega)
and a radius as defined by the "atom_style sphere"_atom_style.html
command.  If the {dipole} keyword is used, then they must also store a
dipole moment as defined by the "atom_style dipole"_atom_style.html
command.

All particles in the group must be finite-size spheres.  They cannot
be point particles.

Use of the {disc} keyword is only allowed for 2d simulations, as
defined by the "dimension"_dimension.html keyword.

[Related commands:]

"fix nve"_fix_nve.html, "fix nve/asphere"_fix_nve_asphere.html

[Default:] none

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:link(nve-Dullweber)
[(Dullweber)] Dullweber, Leimkuhler and McLachlan, J Chem Phys, 107,
5840 (1997).
