# compute plasticity/atom command

## Syntax

``` LAMMPS
compute ID group-ID plasticity/atom
```

-   ID, group-ID are documented in compute command
-   plasticity/atom = style name of this compute command

## Examples

``` LAMMPS
compute 1 all plasticity/atom
```

## Description

Define a computation that calculates the per-atom plasticity for each
atom in a group. This is a quantity relevant for [Peridynamics
models](pair_peri). See [this document](PDF/PDLammps_overview.pdf)\_ for
an overview of LAMMPS commands for Peridynamics modeling.

The plasticity for a Peridynamic particle is the so-called consistency
parameter ($\lambda$). For elastic deformation, $\lambda = 0$, otherwise
$\lambda > 0$ for plastic deformation. For details, see
[(Mitchell)](Mitchell) and the PDF doc included in the LAMMPS
distribution in [doc/PDF/PDLammps_EPS.pdf](PDF/PDLammps_EPS.pdf)\_.

This command can be invoked for one of the Peridynamic [pair
styles](pair_peri): peri/eps.

The plasticity value will be 0.0 for atoms not in the specified compute
group.

## 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 are unitless numbers $\lambda \ge 0.0$.

## Restrictions

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

## Related commands

[compute damage/atom](compute_damage_atom), [compute
dilatation/atom](compute_dilatation_atom)

## Default

none

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

::: {#Mitchell}
**(Mitchell)** Mitchell, \"A non-local, ordinary-state-based
viscoelasticity model for peridynamics\", Sandia National Lab Report,
8064:1-28 (2011).
:::