# compute tdpd/cc/atom command

## Syntax

``` LAMMPS
compute ID group-ID tdpd/cc/atom index
```

-   ID, group-ID are documented in [compute](compute) command
-   tdpd/cc/atom = style name of this compute command
-   index = index of chemical species (1 to Nspecies)

## Examples

``` LAMMPS
compute 1 all tdpd/cc/atom 2
```

## Description

Define a computation that calculates the per-atom chemical concentration
of a specified species for each tDPD particle in a group.

The chemical concentration of each species is defined as the number of
molecules carried by a tDPD particle for dilute solution. For more
details see [(Li2015)](Li2015a).

## 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 the
[Howto output](Howto_output) page for an overview of LAMMPS output
options.

The per-atom vector values will be in the units of chemical species per
unit mass.

## Restrictions

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

## Related commands

[pair_style tdpd](pair_mesodpd)

## Default

none

------------------------------------------------------------------------

::: {#Li2015a}
**(Li2015)** Li, Yazdani, Tartakovsky, Karniadakis, J Chem Phys, 143:
014101 (2015). DOI: 10.1063/1.4923254
:::