[lammps-users] temp/rescale causing energy to drift and velocity problems

Yeah, it turned out that was the problem, I switched over to using the
temp/com compute and that fixed it.


    Have you visualized the simulation? Is it doing what
    you expect. Sometimes you can get a flying-icecube
    effect where the atoms crystallize and the whole chunk
    flies off in some direction. The thermostat will think
    this has a good temperature, so it can sometimes
    actually induce this effect.


    > Hello all,
    > I'm running a small scale (800 atom) simulation and attempting to
    > temperature with the temp/rescale fix:
    > fix 1 all temp/rescale 1 0.5 0.5 0.0 1.0
    > fix 2 all nve
    > The trouble is, after about 10,000,000 timesteps, the potential energy
    > will very rapidly (in about 100,000 timesteps) decay to a much lower
    > (not zero, just down) and also be much less noisy. The velocities also
    > approach a single value after this point. Running with different
    > data files has the same problem, and running at a higher temperature
    > causes it to happen even sooner (8,000,000 or so timesteps in)
    > My first thought was that tightly controlling the temperature that
way was
    > causing the problem, but using:
    > fix 1 all temp/rescale 10 0.5 0.5 0.0 1.0
    > and
    > fix 1 all temp/rescale 1 0.5 0.5 0.005 0.99
    > both caused the energy drift to happen even sooner.
    > Any ideas? Is this a common problem with that thermostat? I've
used the
    > nvt thermostat on the same start up data and it works fine, but I
need a
    > very tight control on the temperature.
    > Jon Brown
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