[lammps-users] ERROR on proc 2: Particle on or inside fix wall surface (../fix_wall_harmonic.cpp:74)

Dear lammps User,
I am using LAMMPS 10-March 2021 version on the ubuntu 20.04 LTS system. I wish to fix the edge of my simulation box using PBC. For this, I used Fix Wall/harmonic command but find the following errors:

Setting up Verlet run …
Unit style : lj
Current step : 0
Time step : 0.005
Per MPI rank memory allocation (min/avg/max) = 5.550 | 5.550 | 5.550 Mbytes
Step Temp TotEng PotEng KinEng Press Volume Density
0 0.020079576 0.50338531 0.48340664 0.019978674 3.6745748 220.99448 0.47148761
ERROR on proc 2: Particle on or inside fix wall surface (…/fix_wall_harmonic.cpp:74)
ERROR on proc 0: Particle on or inside fix wall surface (…/fix_wall_harmonic.cpp:74)

please visualize or manually inspect the generated coordinates. You are creating atoms exactly on the box boundaries and thus on the wall.
also, it makes no sense to have a wall in a direction with periodic boundaries because a) you can have unphysical interactions with periodic images across the wall, and b) atoms can move across the other cell edge to the back of the wall.

axel.