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### fix nve/sphere command

### fix nve/sphere/omp command

Syntax:

    fix ID group-ID nve/sphere

- ID, group-ID are documented in fix command
- nve/sphere = style name of this fix command
- zero or more keyword/value pairs may be appended

      keyword = update
        update value = dipole or dipole/dlm
          dipole = update orientation of dipole moment during integration
          dipole/dlm = use DLM integrator to update dipole orientation

Examples:

    fix 1 all nve/sphere
    fix 1 all nve/sphere update dipole
    fix 1 all nve/sphere update dipole/dlm

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 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 command.

The default dipole orientation integrator can be changed to the Dullweber-Leimkuhler-McLachlan integration scheme (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.

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 in Section 5 of the manual. 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 Making LAMMPS section 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 when you invoke LAMMPS, or you can use the suffix command in your input script.

See Section 5 of the manual for more instructions on how to use the accelerated styles effectively.

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

No information about this fix is written to binary restart files. None of the fix_modify options are relevant to this fix. No global or per-atom quantities are stored by this fix for access by various output commands. No parameter of this fix can be used with the start/stop keywords of the run command. This fix is not invoked during energy minimization.

Restrictions:

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

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

Related commands:

fix nve, fix nve/asphere

Default: none

(Dullweber) Dullweber, Leimkuhler and McLachlan, J Chem Phys, 107, 5840 (1997).