# compute dipole command

# compute dipole/tip4p command

## Syntax

``` LAMMPS
compute ID group-ID style arg
```

-   ID, group-ID are documented in [compute](compute) command
-   style = *dipole* or *dipole/tip4p*
-   arg = *mass* or *geometry* = use COM or geometric center for charged
    chunk correction (optional)

## Examples

``` LAMMPS
compute 1 fluid dipole
compute dw water dipole geometry
compute dw water dipole/tip4p
```

## Description

Define a computation that calculates the dipole vector and total dipole
for a group of atoms.

These computes calculate the x,y,z coordinates of the dipole vector and
the total dipole moment for the atoms in the compute group. This
includes all effects due to atoms passing through periodic boundaries.
For a group with a net charge the resulting dipole is made position
independent by subtracting the position vector of the center of mass or
geometric center times the net charge from the computed dipole vector.
Both per-atom charges and per-atom dipole moments, if present,
contribute to the computed dipole.

::: versionadded
28Mar2023
:::

Compute *dipole/tip4p* includes adjustments for the charge carrying
point M in molecules with TIP4P water geometry. The corresponding
parameters are extracted from the pair style.

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

The coordinates of an atom contribute to the dipole in \"unwrapped\"
form, by using the image flags associated with each atom. See the [dump
custom](dump) command for a discussion of \"unwrapped\" coordinates. See
the Atoms section of the [read_data](read_data) command for a discussion
of image flags and how they are set for each atom. You can reset the
image flags (e.g., to 0) before invoking this compute by using the [set
image](set) command.
::::

## Output info

These computes calculate a global scalar containing the magnitude of the
computed dipole moment and a global vector of length 3 with the dipole
vector. See the [Howto output](Howto_output) page for an overview of
LAMMPS output options.

The computed values are \"intensive\". The array values will be in
dipole units (i.e., charge [units](units) times distance
[units](units)).

## Restrictions

Compute style *dipole/tip4p* is part of the EXTRA-COMPUTE package. It is
only enabled if LAMMPS was built with that package. See the [Build
package](Build_package) page for more info.

Compute style *dipole/tip4p* can only be used with tip4p pair styles.

## Related commands

[compute dipole/chunk](compute_dipole_chunk)

## Default

Using the center of mass is the default setting for the net charge
correction.