# compute cluster/atom command

## Syntax

    compute ID group-ID cluster/atom general_keyword general_values cutoff

- ID, group-ID are documented in compute command
- cluster/atom = style name of this compute command
- general_keywords general_values are documented in compute
- cutoff = distance within which to label atoms as part of same cluster (distance units)

## Examples

    compute 1 all cluster/atom 1.0

## Description

Define a computation that assigns each atom a cluster ID.

A cluster is defined as a set of atoms, each of which is within the cutoff distance from one or more other atoms in the cluster. If an atom has no neighbors within the cutoff distance, then it is a 1-atom cluster. The ID of every atom in the cluster will be the smallest atom ID of any atom in the cluster.

Only atoms in the compute group are clustered and assigned cluster IDs. Atoms not in the compute group are assigned a cluster ID = 0.

The neighbor list needed to compute this quantity is constructed each time the calculation is performed (i.e. each time a snapshot of atoms is dumped). Thus it can be inefficient to compute/dump this quantity too frequently or to have multiple compute/dump commands, each of a clsuter/atom style.

## Output info

This compute calculates a per-atom vector, which can be accessed by any command that uses per-atom values from a compute as input. See Section_howto 15 for an overview of LIGGGHTS(R)-PUBLIC output options.

The per-atom vector values will be an ID > 0, as explained above.

## Restrictions

> none

## Related commands

compute coord/atom

Default: none