"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)

:line

compute dilatation/atom command :h3

[Syntax:]

compute ID group-ID dilatation/atom :pre

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

[Examples:]

compute 1 all dilatation/atom :pre

[Description:]

Define a computation that calculates the per-atom dilatation for each
atom in a group.  This is a quantity relevant for "Peridynamics
models"_pair_peri.html.  See "this document"_PDF/PDLammps_overview.pdf
for an overview of LAMMPS commands for Peridynamics modeling.

For small deformation, dilatation of is the measure of the volumetric
strain.

The dilatation "theta" for each peridynamic particle I is calculated
as a sum over its neighbors with unbroken bonds, where the
contribution of the IJ pair is a function of the change in bond length
(versus the initial length in the reference state), the volume
fraction of the particles and an influence function.  See the
"PDLAMMPS user
guide"_http://www.sandia.gov/~mlparks/papers/PDLAMMPS.pdf for a formal
definition of dilatation.

This command can only be used with a subset of the Peridynamic "pair
styles"_pair_peri.html: peri/lps, peri/ves and peri/eps.

The dilatation 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
Section_howto 15 for an overview of LAMMPS output options.

The per-atom vector values are unitlesss numbers (theta) >= 0.0.

[Restrictions:]

This compute is part of the PERI package.  It is only enabled if
LAMMPS was built with that package.  See the "Making
LAMMPS"_Section_start.html#start_3 section for more info.

[Related commands:]

"compute damage"_compute_damage.html, "compute
plasticity"_compute_plasticity.html

[Default:] none 
