"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)

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pair_style peri/pmb command :h3
pair_style peri/pmb/omp command :h3
pair_style peri/lps command :h3
pair_style peri/lps/omp command :h3
pair_style peri/ves command :h3

[Syntax:]

pair_style style :pre 

style = {peri/pmb} or {peri/lps} or {peri/ves} :ul

[Examples:]

pair_style peri/pmb
pair_coeff * * 1.6863e22 0.0015001 0.0005 0.25 :pre

pair_style peri/lps
pair_coeff * * 14.9e9 14.9e9 0.0015001 0.0005 0.25 :pre

pair_style peri/ves
pair_coeff * * 14.9e9 14.9e9 0.0015001 0.0005 0.25 0.5 0.001 :pre

[Description:]

The peridynamic pair styles implement material models that can be used
at the mescscopic and macroscopic scales.

Style {peri/pmb} implements the Peridynamic bond-based prototype
microelastic brittle (PMB) model.

Style {peri/lps} implements the Peridynamic state-based linear
peridynamic solid (LPS) model.

Style {peri/ves} implements the Peridynamic state-based linear
peridynamic viscoelastic solid (VES) model.

The canonical papers on Peridynamics are "(Silling 2000)"_#Silling2000
and "(Silling 2007)"_#Silling2007.  The implementation of Peridynamics
in LAMMPS is described in "(Parks)"_#Parks.  Also see the "PDLAMMPS
user guide"_http://www.sandia.gov/~mlparks/papers/PDLAMMPS.pdf for
more details about the implementation of peridynamics in LAMMPS.

The peridynamic VES model in PDLAMMPS is implemented by R. Rahman and
J.T Foster at University of Texas at San Antonio. The VES formulation
is described in "(Mitchell)"_#Mitchell.  An additional PDF doc with
details is in "doc/PDF/PDLammps_VES.pdf"_PDF/PDLammps_VES.pdf.  For
questions regarding VES implementation in LAMMPS please contact Rezwan
Rahman: rezwanur.rahman at utsa.edu.

The following coefficients must be defined for each pair of atom types
via the "pair_coeff"_pair_coeff.html command as in the examples above,
or in the data file or restart files read by the
"read_data"_read_data.html or "read_restart"_read_restart.html
commands, or by mixing as described below.

For the {peri/pmb} style:

c (energy/distance/volume^2 units)
horizon (distance units)
s00 (unitless)
alpha (unitless) :ul

C is the effectively a spring constant for Peridynamic bonds, the
horizon is a cutoff distance for truncating interactions, and s00 and
alpha are used as a bond breaking criteria.  The units of c are such
that c/distance = stiffness/volume^2, where stiffness is
energy/distance^2 and volume is distance^3.  See the users guide for
more details.

For the {peri/lps} style:

K (force/area units)
G (force/area units)
horizon (distance units)
s00 (unitless)
alpha (unitless) :ul

K is the bulk modulus and G is the shear modulus.  The horizon is a
cutoff distance for truncating interactions, and s00 and alpha are
used as a bond breaking criteria. See the users guide for more
details.

For the {peri/ves} style:

K (force/area units)
G (force/area units)
horizon (distance units)
s00 (unitless)
alpha (unitless) 
m_lambdai (unitless)
m_taubi (unitless) :ul

The same as for {peri/lps}, K is the bulk modulus and G is the shear
modulus. The horizon is a cutoff distance for truncating interactions,
and s00 and alpha are used as a bond breaking criteria. m_lambdai and
m_taubi are the viscoelastic relaxation parameter and time constant,
respectively. m_lambdai varies within zero to one. For very small
values of m_lambdai the viscoelsatic model responds very similar to a
linear elastic model. For details see the description in
"(Mitchell)"_#Mitchell.

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Styles with a {cuda}, {gpu}, {omp}, or {opt} suffix are functionally
the same as the corresponding style without the suffix.  They have
been optimized to run faster, depending on your available hardware, as
discussed in "Section_accelerate"_Section_accelerate.html of the
manual.  The accelerated styles take the same arguments and should
produce the same results, except for round-off and precision issues.

These accelerated styles are part of the USER-CUDA, GPU, USER-OMP and OPT
packages, respectively.  They are only enabled if LAMMPS was built with
those packages.  See the "Making LAMMPS"_Section_start.html#start_3
section for more info.

You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the "-suffix command-line
switch"_Section_start.html#start_7 when you invoke LAMMPS, or you can
use the "suffix"_suffix.html command in your input script.

See "Section_accelerate"_Section_accelerate.html of the manual for
more instructions on how to use the accelerated styles effectively.

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[Mixing, shift, table, tail correction, restart, rRESPA info]:

These pair styles do not support mixing.  Thus, coefficients for all
I,J pairs must be specified explicitly.

These pair styles do not support the "pair_modify"_pair_modify.html
shift option.

The "pair_modify"_pair_modify.html table and tail options are not
relevant for these pair styles.

These pair styles write their information to "binary restart
files"_restart.html, so pair_style and pair_coeff commands do not need
to be specified in an input script that reads a restart file.

These pair styles can only be used via the {pair} keyword of the
"run_style respa"_run_style.html command.  They do not support the
{inner}, {middle}, {outer} keywords.

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[Restrictions:]

The {peri/pmb}, {peri/lps} and {peri/ves} styles are part of the PERI
package. They are only enabled if LAMMPS was built with that package.
See the "Making LAMMPS"_Section_start.html#start_3 section for more
info.

[Related commands:]

"pair_coeff"_pair_coeff.html

[Default:] none

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:link(Parks)
[(Parks)] Parks, Lehoucq, Plimpton, Silling, Comp Phys Comm, 179(11),
777-783 (2008).

:link(Silling2000)
[(Silling 2000)] Silling, J Mech Phys Solids, 48, 175-209 (2000).

:link(Silling2007)
[(Silling 2007)] Silling, Epton, Weckner, Xu, Askari, J Elasticity,
88, 151-184 (2007).

:link(Mitchell)
[(Mitchell)] Mitchell, "A non-local, ordinary-state-based
viscoelasticity model for peridynamics", Sandia National Lab Report,
8064:1-28 (2011).
