[lammps-users] compute force bewteen groups (Yi Dong)

Dear Steve and Ian,

Concerning the interaction force between Al bulk and Si indenter, if you conduct the indentation simulation with “fix indent” command, you can get that force via commands as follows:
fix_modify ID energy yes; thermo_style custom step f_ID[1/2/3]. The ID is the ID for the fix indent.

However, Steve, I also have a question about that. I get that force successfully in that way when the indenter penetrates into the bulk material, but the three force vectors are all zero when the indenter withdrawed from the bulk material. Do you have such experience?

Best regards,

Fix indent pushes an idealized geometric indenter (no atoms)
into a material. That would not be a Si indenter with MEAM
atoms interacting with the bulk. But you should still be able
to sum the total force on indenter atoms to get net force
on the indenter (as I emailed before).

Re: zero indenter force on removal, can you post a simple
example with output? It could be that very shortly after
you begin to withdraw, there is no overlap of the indenter with
atoms (esp in a solid), in which case there is no longer any