# compute ke/atom/eff command

## Syntax

``` LAMMPS
compute ID group-ID ke/atom/eff
```

-   ID, group-ID are documented in [compute](compute) command
-   ke/atom/eff = style name of this compute command

## Examples

``` LAMMPS
compute 1 all ke/atom/eff
```

## Description

Define a computation that calculates the per-atom translational (nuclei
and electrons) and radial kinetic energy (electron only) in a group. The
particles are assumed to be nuclei and electrons modeled with the
[electronic force field](pair_eff).

The kinetic energy for each nucleus is computed as $\frac{1}{2} m
v^2$, where *m* corresponds to the corresponding nuclear mass, and the
kinetic energy for each electron is computed as $\frac{1}{2} (m_e
v^2 + \frac{3}{4} m_e s^2)$, where $m_e$ and *v* correspond to the mass
and translational velocity of each electron, and *s* to its radial
velocity, respectively.

There is a subtle difference between the quantity calculated by this
compute and the kinetic energy calculated by the *ke* or *etotal*
keyword used in thermodynamic output, as specified by the
[thermo_style](thermo_style) command. For this compute, kinetic energy
is \"translational\" plus electronic \"radial\" kinetic energy,
calculated by the simple formula above. For thermodynamic output, the
*ke* keyword infers kinetic energy from the temperature of the system
with $\frac{1}{2} k_B T$ of energy for each (nuclear-only) degree of
freedom in eFF.

:::: note
::: title
Note
:::

The temperature in eFF should be monitored via the [compute
temp/eff](compute_temp_eff) command, which can be printed with
thermodynamic output by using the [thermo_modify](thermo_modify)
command, as shown in the following example:
::::

``` LAMMPS
compute         effTemp all temp/eff
thermo_style    custom step etotal pe ke temp press
thermo_modify   temp effTemp
```

The value of the kinetic energy will be 0.0 for atoms (nuclei or
electrons) not in the specified compute group.

## Output info

This compute calculates a scalar quantity for each atom, which can be
accessed by any command that uses per-atom computes as input. See the
[Howto output](Howto_output) page for an overview of LAMMPS output
options.

The per-atom vector values will be in energy [units](units).

## Restrictions

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

## Related commands

[dump custom](dump)

## Default

none