[lammps-users] How to modify the boundary of a box?


I have a very specific problem

I want to apply the fix box/relax command to define a stress distribution on my granular sample. After the compaction I want to identify a particular region on a side of a box (say a circular region) and make it “inert” to the contact mechanics with the granular sample.

I mean if there is an atom (grain) in contact with that specific region then no stress should be applied to that atom (grain). It would be highly helpful if that specific region would not interact at all with the atom.

I know I can make any sort of geometry at the wall if I am okay with a rough wall. But I want a more accurate representation of a hole in the wall and not deal with approximations. A region defined on the wall that would not allow any contact forces to be applied to the grains in contact should also work. I want to maintain the stress conditions in the rest of the portion of the wall though.

Thank you for your help in advance

Ripudaman Manchanda

If you want an ideal wall that has some non-interacting patch, I think
you'd have to modify fix wall/gran to check for that geometry
and do the right thing.