[lammps-users] Is "displace_atoms" command truncating small increments?


I want to shift a group of atoms by a certain distance periodically over the course of a simulation. I am attempting to use the "displace_atoms" command, but I am encountering a problem that seems to depend on the size of the displacement. Using displace_atoms with increments > 0.1 angstrom works fine, as shown in the video at the link below.


...However, increments less than 0.05 angstrom do not advance the selected group of atoms (in the pink substrate) at all. My questions are: Why doesn't the system get traction with smaller increments? Should I use a different LAMMPS command to accomplish this?

Nicholas J. Lee

More info: The displacements in the video are 0.1 angstrom every 10 time steps, where 1 ts = 2 fs. But the video is only a demo, it's much faster than I want. I would like to displace at rates like 0.05 angstroms per 5000 ts (or other quotients that average to > 5 m/s).

There is no truncation in displace_atoms, so something else must be
happening in your system. Have you dumped atoms before and
after the displace to verify they are not moving?