Dear Users,
I ran into a particular issue in my system that I could not quite figure out. My system consists of 2D Gay-Berne particles (3:1 aspect ratio) with two patches attached to each of them. I am studying how the system would be in a very high temperature setting (like T = 10 to 100). I am running the simulation at T = 24, and I noticed that the temperature output is much higher than my input temperature.
So I tried a different thermostat (Langevin), and there I also noticed that depending on the dampening factor, the temperature fluctuates near my input temperature for a while and then goes up again.
What could be causing this issue?
I ran the same simulation without the patches, and this issue did not occur. Is the method of inclusion of patches in my system wrong? If so, how could I rectify it?
Code for the patchy gay-berne system:
in.patch (2.2 KB)
patchy_gb.txt (155.5 KB)
Code without the patches:
gb.txt (58.2 KB)
in.gb (1.4 KB)
You need to rule out numerical heating–if your timestep is too large then the system won’t conserve energy. You need a smaller timestep as the temperature goes up.
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I tried this one. I reduced the timestep to a really low value(0.00001), but the temperature eventually shoots up.
As a check, you should remove the thermostat and use fix nve integrator to see if your system conserves energy. If it does not, then there is something wrong with your model or simulation setup.
As @stamoor already mentioned, this is not likely a problem of the thermostat but a symptom of bad potential parameters or a badly designed model. It is not likely that you’ll find somebody that will debug other people’s inputs unless you can prove beyond doubt that it is due to a bug in LAMMPS, i.e. where it does not behave according to the documentation (that is usually difficult to do, and just stating that the simulation crashes is not sufficient).