# fix nve/eff command

## Syntax

fix ID group-ID nve/eff

• ID, group-ID are documented in fix command
• nve/eff = style name of this fix command

## Examples

fix 1 all nve/eff


## Description

Perform constant NVE integration to update position and velocity for nuclei and electrons in the group for the electron force field model. V is volume; E is energy. This creates a system trajectory consistent with the microcanonical ensemble.

The operation of this fix is exactly like that described by the fix nve command, except that the radius and radial velocity of electrons are also updated.

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 is part of the USER-EFF package. It is only enabled if LAMMPS was built with that package. See the Build package doc page for more info.