Dear Christoph, dear Andreas,
Could you please provide some reference(s) that use(s) or derive(s) the equations of the cohesion models used in LIGGGHTS (skrj and skrj2 equations; see below)?
Thanks so much!
A simple linear cohesion model can be activated by setting cohesion = 'sjkr' or 'sjkr2' (simplified Johnson-Kendall-Roberts model). 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. For sjkr2, the sphere-sphere contact area is calculated as
A = 2*Pi * delta_n * (2R*)
If you are using the linear cohesion 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)