# fix nve/sphere 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
      dipole = update orientation of dipole moment during integration

## Examples

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

## 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 particles via use of the atom_style dipole command.

## 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