# fix nve/tri command

## Syntax

    fix ID group-ID nve/tri

-   ID, group-ID are documented in [fix](fix) command
-   nve/tri = style name of this fix command

## Examples

``` LAMMPS
fix 1 all nve/tri
```

## Description

Perform constant NVE integration to update position, velocity,
orientation, and angular momentum for triangular particles in the group
each timestep. V is volume; E is energy. This creates a system
trajectory consistent with the microcanonical ensemble. See the [Howto
spherical](Howto_spherical) page for an overview of using triangular
particles.

This fix differs from the [fix nve](fix_nve) command, which assumes
point particles and only updates their position and velocity.

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

No information about this fix is written to [binary restart
files](restart). None of the [fix_modify](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](Howto_output). No
parameter of this fix can be used with the *start/stop* keywords of the
[run](run) command. This fix is not invoked during [energy
minimization](minimize).

## Restrictions

This fix is part of the ASPHERE package. It is only enabled if LAMMPS
was built with that package. See the [Build package](Build_package) page
for more info.

This fix requires that particles be triangles as defined by the
[atom_style tri](atom_style) command.

## Related commands

[fix nve](fix_nve), [fix nve/asphere](fix_nve_asphere)

## Default

none