I was wondering if anyone had seen something like this before. I'm running on a 2x4x1 MPI grid. I use the "soft" potential with an energy scale of 1.0 a binary size distribution (radius=.3, radius=.5) with about 108,000 atoms. The initial configuration is completely random (generated by hand). I have a zero temperature langevin thermostat with timeconstant 1.0.
By the end of 5000 timesteps the large particles seem to have segregated to the processor boundaries (see image below --- big guys are white... little guys are green). Worse yet at about 9000 timesteps, I get an "ERROR: lost atom" message and LAMMPS terminates. Temperature and potential energy look very sane at that point expect for a NaN in the temperature column at the very last step (divide by zero somewhere?).
I have not run a system of this size on a single CPU, but I *have* run a virtually identical system with 1/4 the particles on a single CPU (not using MPI, but using the included "STUBS" library) and have not had these kinds of problems.
Anyone have any ideas as to what I might be doing wrong?
I am not using the most current version of LAMMPS (which Steve posted last week). I will upgrade at some point today and try again.
input3 (466 Bytes)
output3.gz (176 KB)
dump3.tiff (298 KB)