LIGGGHTS WWW Site - LAMMPS WWW Site - LIGGGHTS Documentation - LIGGGHTS Commands

### gran cohesion sjkr

Syntax:

    cohesion sjkr

LIGGGHTS vs. LAMMPS Info:

This part of pair gran and fix wall/gran is not availabe in LAMMPS.

Description:

This model can be used as part of pair gran and fix wall/gran

The simplified JKR - Johnson-Kendall-Roberts (SJKR) model adds an additional normal force contribution. If two particle are in contact, it adds an additional normal force tending to maintain the contact, which writes

F = k A,

where A is the particle contact area and k is the cohesion energy density in J/m3. For sjkr, the sphere-sphere contact area is calculated as (http://mathworld.wolfram.com/Sphere-SphereIntersection.html)

A = Pi/4 * ((dist-Ri-Rj)*(dist+Ri-Rj)*(dist-Ri+Rj)*(dist+Ri+Rj) )/(dist*dist)

where dist is the distance between the particle centers.

If you are using the SJKR model, you must also define the cohesion energy density:

    fix id all property/global cohesionEnergyDensity peratomtypepair n_atomtypes value_11 value_12 .. value_21 value_22 .. .
        (value_ij=value for the cohesion energy density (in Energy/Length3 units) between atom type i and j; n_atomtypes is the number of atom types you want to use in your simulation)

IMPORTANT NOTE: You have to use atom styles beginning from 1, e.g. 1,2,3,...

Restrictions:

The cohesion model has been derived for the Hertzian Style, it may note be appropriate for the Hookean styles.