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<HTML>
<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
</CENTER>
<HR>
<H3>pair_style peri/pmb command
</H3>
<H3>pair_style peri/pmb/omp command
</H3>
<H3>pair_style peri/lps command
</H3>
<H3>pair_style peri/lps/omp command
</H3>
<H3>pair_style peri/ves command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>pair_style style
</PRE>
<UL><LI>style = <I>peri/pmb</I> or <I>peri/lps</I> or <I>peri/ves</I>
</UL>
<P><B>Examples:</B>
</P>
<PRE>pair_style peri/pmb
pair_coeff * * 1.6863e22 0.0015001 0.0005 0.25
</PRE>
<PRE>pair_style peri/lps
pair_coeff * * 14.9e9 14.9e9 0.0015001 0.0005 0.25
</PRE>
<PRE>pair_style peri/ves
pair_coeff * * 14.9e9 14.9e9 0.0015001 0.0005 0.25 0.5 0.001
</PRE>
<P><B>Description:</B>
</P>
<P>The peridynamic pair styles implement material models that can be used
at the mescscopic and macroscopic scales.
</P>
<P>Style <I>peri/pmb</I> implements the Peridynamic bond-based prototype
microelastic brittle (PMB) model.
</P>
<P>Style <I>peri/lps</I> implements the Peridynamic state-based linear
peridynamic solid (LPS) model.
</P>
<P>Style <I>peri/ves</I> implements the Peridynamic state-based linear
peridynamic viscoelastic solid (VES) model.
</P>
<P>The canonical papers on Peridynamics are <A HREF = "#Silling2000">(Silling 2000)</A>
and <A HREF = "#Silling2007">(Silling 2007)</A>. The implementation of Peridynamics
in LAMMPS is described in <A HREF = "#Parks">(Parks)</A>. Also see the <A HREF = "http://www.sandia.gov/~mlparks/papers/PDLAMMPS.pdf">PDLAMMPS
user guide</A> for
more details about the implementation of peridynamics in LAMMPS.
</P>
<P>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 <A HREF = "#Mitchell">(Mitchell)</A>. An additional PDF doc with
details is in <A HREF = "PDF/PDLammps_VES.pdf">doc/PDF/PDLammps_VES.pdf</A>. For
questions regarding VES implementation in LAMMPS please contact Rezwan
Rahman: rezwanur.rahman at utsa.edu.
</P>
<P>The following coefficients must be defined for each pair of atom types
via the <A HREF = "pair_coeff.html">pair_coeff</A> command as in the examples above,
or in the data file or restart files read by the
<A HREF = "read_data.html">read_data</A> or <A HREF = "read_restart.html">read_restart</A>
commands, or by mixing as described below.
</P>
<P>For the <I>peri/pmb</I> style:
</P>
<UL><LI>c (energy/distance/volume^2 units)
<LI>horizon (distance units)
<LI>s00 (unitless)
<LI>alpha (unitless)
</UL>
<P>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.
</P>
<P>For the <I>peri/lps</I> style:
</P>
<UL><LI>K (force/area units)
<LI>G (force/area units)
<LI>horizon (distance units)
<LI>s00 (unitless)
<LI>alpha (unitless)
</UL>
<P>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.
</P>
<P>For the <I>peri/ves</I> style:
</P>
<UL><LI>K (force/area units)
<LI>G (force/area units)
<LI>horizon (distance units)
<LI>s00 (unitless)
<LI>alpha (unitless)
<LI>m_lambdai (unitless)
<LI>m_taubi (unitless)
</UL>
<P>The same as for <I>peri/lps</I>, 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
<A HREF = "#Mitchell">(Mitchell)</A>.
</P>
<HR>
<P>Styles with a <I>cuda</I>, <I>gpu</I>, <I>omp</I>, or <I>opt</I> 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 <A HREF = "Section_accelerate.html">Section_accelerate</A> of the
manual. The accelerated styles take the same arguments and should
produce the same results, except for round-off and precision issues.
</P>
<P>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 <A HREF = "Section_start.html#start_3">Making LAMMPS</A>
section for more info.
</P>
<P>You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the <A HREF = "Section_start.html#start_7">-suffix command-line
switch</A> when you invoke LAMMPS, or you can
use the <A HREF = "suffix.html">suffix</A> command in your input script.
</P>
<P>See <A HREF = "Section_accelerate.html">Section_accelerate</A> of the manual for
more instructions on how to use the accelerated styles effectively.
</P>
<HR>
<P><B>Mixing, shift, table, tail correction, restart, rRESPA info</B>:
</P>
<P>These pair styles do not support mixing. Thus, coefficients for all
I,J pairs must be specified explicitly.
</P>
<P>These pair styles do not support the <A HREF = "pair_modify.html">pair_modify</A>
shift option.
</P>
<P>The <A HREF = "pair_modify.html">pair_modify</A> table and tail options are not
relevant for these pair styles.
</P>
<P>These pair styles write their information to <A HREF = "restart.html">binary restart
files</A>, so pair_style and pair_coeff commands do not need
to be specified in an input script that reads a restart file.
</P>
<P>These pair styles can only be used via the <I>pair</I> keyword of the
<A HREF = "run_style.html">run_style respa</A> command. They do not support the
<I>inner</I>, <I>middle</I>, <I>outer</I> keywords.
</P>
<HR>
<P><B>Restrictions:</B>
</P>
<P>The <I>peri/pmb</I>, <I>peri/lps</I> and <I>peri/ves</I> styles are part of the PERI
package. They are only enabled if LAMMPS was built with that package.
See the <A HREF = "Section_start.html#start_3">Making LAMMPS</A> section for more
info.
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "pair_coeff.html">pair_coeff</A>
</P>
<P><B>Default:</B> none
</P>
<HR>
<A NAME = "Parks"></A>
<P><B>(Parks)</B> Parks, Lehoucq, Plimpton, Silling, Comp Phys Comm, 179(11),
777-783 (2008).
</P>
<A NAME = "Silling2000"></A>
<P><B>(Silling 2000)</B> Silling, J Mech Phys Solids, 48, 175-209 (2000).
</P>
<A NAME = "Silling2007"></A>
<P><B>(Silling 2007)</B> Silling, Epton, Weckner, Xu, Askari, J Elasticity,
88, 151-184 (2007).
</P>
<A NAME = "Mitchell"></A>
<P><B>(Mitchell)</B> Mitchell, "A non-local, ordinary-state-based
viscoelasticity model for peridynamics", Sandia National Lab Report,
8064:1-28 (2011).
</P>
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