Here one may find simple examples showing how "fix wall/ess" and "fix wall/region/ess" work. --in.fix_wall_region: This input uses "Data_region" to setup a system of three particles colliding with a cubic region which its walls interact with particle with EES potential. To find out details of how to set parameters of "fix wall/region/ees" see documentation. --in.fix_wall This input uses "Data_wall" to confine a ellipsoidal particle between two EES walls. For more details lookup LAMMPS's documentation under "fix wall/ess" command.