[lammps-users] problem with the neigh_modify command

Hi all,
i'm a new user of lammps code, and we have to simulate a gaseous flow in a microchanel, some atoms of gas between two region, we apply a velocity on the upper region for to displace the gaz and to obtain his velocity profile. We don't have a problem until this point, but when we build an atomic wall structure around the box, for to maintain a realistic gas solid interaction, we have some problem with the the neighbor list build.
After the execution, the program create an orthogonal box with the specific dimension that we want, it also create the atoms, but the problem is on two points:
       1st point: The program running normally but we a have a lost of atoms and a number of
                         dangerous build equal to the neighbor list builds and also a significant lost of atoms.

       2nd point: We make a modification at the neigh_modify command, and after we have a message:
                          ERROR: Illegal neigh_modify command.

Can anybody help me to resolve this problem ?

Thanks in advance.

1st point: You typically lose atoms b/c they move too far, too fast. Dangerous
reneighboring are an indication this is happening. So they don't interact
correctly (not in the neighbor list), and atoms get blown out of the simulation.

2nd point: If you're saying you changed the code, and now it doesn't work,
I can't help with that. Sounds like a parsing problem, if you changed
the syntax.