\(\renewcommand{\AA}{\text{Å}}\)

pair_style bpm/peri command

Syntax

pair_style bpm/peri

Examples

pair_style bpm/peri
pair_coeff * * 1.6863e22 0.0015001

Description

Added in version TBD.

Style bpm/peri supplies the short-range repulsive contact force between non-bonded peridynamic nodes for the bond_style bpm/peri model. It is the BPM-framework equivalent of the contact term built into the legacy peridynamic pair styles. Bonded pairs are handled entirely by the bond style and are excluded here through the 1-2 special_bonds weight; this pair style therefore acts only between nodes that are not bonded (for example new contacts that form after fracture or large deformation).

For a pair of non-bonded nodes within the contact distance \(d = 1.35\, l_c\) (where \(l_c\) is the lattice spacing) the force has magnitude

\[F = 15\, k\, \bar{V}\, \frac{r - d}{\delta}\]

where k is the contact stiffness, \(\delta\) the horizon, \(r\) the current distance, and \(\bar{V} = (V_i + V_j)/2\) the mean nodal volume of the two nodes (read from the per-atom vfrac property declared for the bond style). The factor 15 follows the EMU Theory Manual convention used by the legacy peridynamic styles.

The following coefficients must be defined for each pair of atom types via the pair_coeff command as in the example above, or in the restart files read by the read_restart command:

  • k (energy/distance/volume^2 units), contact stiffness

  • horizon \(\delta\) (distance units)

Typically k and the horizon are set equal to the corresponding bond_coeff values.

Mixing, shift, table, tail correction, restart, rRESPA info

This pair style does not support mixing. Coefficients for all I,J pairs must be specified explicitly.

This pair style does not support the pair_modify shift, table, or tail options.

This pair style writes its 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.

This pair style can only be used via the pair keyword of the run_style respa command. It does not support the inner, middle, outer keywords.

Restrictions

This pair style is part of the BPM package. It is only enabled if LAMMPS was built with that package. See the Build package page for more info.

This pair style requires a per-atom vfrac property (a fix property/atom d_vfrac with ghost communication) and a cubic lattice with equal spacing in x, y, and z. It is intended to be used together with bond_style bpm/peri; see the peridynamics Howto.

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