# compute temp/drude command

## Syntax

``` LAMMPS
compute ID group-ID temp/drude
```

-   ID, group-ID are documented in [compute](compute) command
-   temp/drude = style name of this compute command

## Examples

``` LAMMPS
compute TDRUDE all temp/drude
```

Example input scripts available:
`examples/PACKAGES/drude`{.interpreted-text role="file"}.

## Description

Define a computation that calculates the temperatures of core\--Drude
pairs. This compute is designed to be used with the [thermalized Drude
oscillator model](Howto_drude). Polarizable models in LAMMPS are
described on the [Howto polarizable](Howto_polarizable) doc page.

Drude oscillators consist of a core particle and a Drude particle
connected by a harmonic bond, and the relative motion of these Drude
oscillators is usually maintained cold by a specific thermostat that
acts on the relative motion of the core\--Drude particle pairs.
Therefore, because LAMMPS considers Drude particles as normal atoms in
its default temperature compute ([compute temp](compute_temp) command),
the reduced temperature of the core\--Drude particle pairs is not
calculated correctly.

By contrast, this compute calculates the temperature of the cores using
center-of-mass velocities of the core\--Drude pairs, and the reduced
temperature of the Drude particles using the relative velocities of the
Drude particles with respect to their cores. Non-polarizable atoms are
considered as cores. Their velocities contribute to the temperature of
the cores.

## Output info

This compute calculates a global scalar (the temperature) and a global
vector of length 6, which can be accessed by indices 1\--6, whose
components are

1.  temperature of the centers of mass (temperature units)
2.  temperature of the dipoles (temperature units)
3.  number of degrees of freedom of the centers of mass
4.  number of degrees of freedom of the dipoles
5.  kinetic energy of the centers of mass (energy units)
6.  kinetic energy of the dipoles (energy units)

These values can be used by any command that uses global scalar or
vector values from a compute as input. See the [Howto
output](Howto_output) page for an overview of LAMMPS output options.

Both the scalar value and the first two values of the vector calculated
by this compute are \"intensive\". The other four vector values are
\"extensive\".

## Restrictions

The number of degrees of freedom contributing to the temperature is
assumed to be constant for the duration of the run unless the
*fix_modify* command sets the option *dynamic yes*.

## Related commands

[fix drude](fix_drude), [fix langevin/drude](fix_langevin_drude), [fix
drude/transform](fix_drude_transform), [pair_style thole](pair_thole),
[compute temp](compute_temp)

## Default

none