LubricateU model with simple shear gives particle overlaps

I suggest posting back to the list, I am sure Jeremy or others can probably help you out better than I. Jeremy has helped me in the past. The scripts that I have used inevitably use more pair styles in conjunction with pair lubricate.

There are a couple of factors that could cause your overlaps, and I think they come down to one of two situations. Your force does not become sufficiently high to prevent overlaps due to highly constrained motion as a result of your high density(i.e. excluded volume effects), or that you are not sufficiently resolving the dynamics of the approaching spheres. The first is solved by choosing a smaller cut-inner (a tenth of the diameter is actually quite large), and the latter is just a time-step issue.

You might try shearing at lower densities and a small cut-inner to eliminate the first situation.

Declaring the diameter as 1 doesn’t seem to make a difference compared to using the default value of 1. Do you have any >examples of lubricate/lubricateU scripts that will not allow overlapping, without using a 2nd pair style?

No, I think you always have to use lubricate or lubricateU with another pair style
that provides the core/core interaction and keeps the particles
from overlapping. You’re also required to use atom_style sphere
which is what provides the diameter of the particles. The core/core
interaction (e.g. pair lj/cut or pair colloid) needs to be stiff enough
to insure no pair of particles overlaps at their diameter.


This may be true from a numerical perspective. But the analytic lubrication force used in FLD is singular at contact. You may also lose distinctive features of Stokesian Dynamics if a conservative potential is used here instead. Interactions in FLD are ‘reversible’ in the sense that it takes just as much energy to remove initially close particles as it does to bring particles close to one another.