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### pair_style peri/pmb command

### pair_style peri/pmb/omp command

### pair_style peri/lps command

### pair_style peri/lps/omp command

### pair_style peri/ves command

Syntax:

    pair_style style

- style = peri/pmb or peri/lps or peri/ves

Examples:

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

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

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

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) and (Silling 2007). The implementation of Peridynamics in LAMMPS is described in (Parks). Also see the PDLAMMPS user guide 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). An additional PDF doc with details is in doc/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 command as in the examples above, or in the data file or restart files read by the read_data or read_restart 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)

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)

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)

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).

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 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 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 when you invoke LAMMPS, or you can use the suffix command in your input script.

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

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 shift option.

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

These pair styles write their information to binary restart files, 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 command. They do not support the inner, middle, outer keywords.

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 for more info.

Related commands:

pair_coeff

Default: none

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

(Silling 2000) Silling, J Mech Phys Solids, 48, 175-209 (2000).

(Silling 2007) Silling, Epton, Weckner, Xu, Askari, J Elasticity, 88, 151-184 (2007).

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