Yeah, it turned out that was the problem, I switched over to using the
temp/com compute and that fixed it.
Jon
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.
Steve
> Hello all,
>
> I'm running a small scale (800 atom) simulation and attempting to
control
> 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
value
> (not zero, just down) and also be much less noisy. The velocities also
> approach a single value after this point. Running with different
starting
> 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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