I am having trouble with LAMMPS losing atoms. I am running irradiation damage cascades, and when my primary knock-ok atom's (PKA) energy gets above a certain threshold, I can't avoid getting the lost atoms error. I remedied this for a while by changing the timestep size to smaller and smaller values, but that is not working anymore. My current timestep is .00001 ps, but I have tried even smaller with no help. In the literature, other people have been using 1 fs without issue (with other codes), so I don't think my timestep is unreasonable. Here is some of the output:
1418 223.27989 -526364.75 0 -522670.54 4234.8036
1419 221.30761 -526332.1 0 -522670.53 4241.7577
1420 3.5804153e+21 3.1764699e+11 0 5.9238577e+22 4.2470611e+22
WARNING: Lost atoms: original 128000 current 127998
1421 76.642234 -527533.49 0 -526265.43 1231.472
1422 76.615982 -527533.06 0 -526265.43 1231.8653
1423 76.590123 -527532.63 0 -526265.43 1232.2527
I switched to warn mode for lost atoms, for debugging. As you can see, the temperature, and all other values jump dramatically before the atoms are lost. All other atoms start at 0 K, except the PKA. I have tried changing the direction of the PKA, but it just changes the point in time at which I encounter the error. My PKA has velocity of 5 keV, so about 400 lattice spacings/ps in the fastest component of velocity.
I am using an eam/fs potential (Fe_mm.eam.fs), the well-known Ackland potential for iron. Any suggestions?
Grad Student - Nuclear Engineering