Temperature has exceeded maximum allowed set by mdmaxtemp

When run the melocular dynamics by the GULP with different Forcefield, I usually met the error " temperature has exceeded maximum allowed set by mdmaxtemp ". Such as for the magnesite with the Carbonate forcefield. I try to change the temperature and the timestep. The run show the same error. Do some body help me to find the reason for this error. Thanks.

There are many possible causes including the most common ones:

  1. An error in specifying the force field
  2. Starting from a high energy configuration so that the system dumps internal energy into kinetic faster than your specified thermostat can remove it with the parameters you’ve specified.
  3. System size is too small leading to large fluctuations
    Hope that helps,

Thank you so much, dear Julian, I met the question during a lot gulp run or simulation. I try to change the system size and force field, temperature and time step, but it is very hart to get ideal and reasonable results. I will follow your advices and try again.
Thank you again.

It shouldn’t be too hard to get reasonable results given that there is a large literature on simulating this type of system already. You can check the force field by comparing to the published results in optimisation. If you then start the simulation from the optimised structure then you shouldn’t overheat if your time step is sensible (you can find reasonable values from the literature) and your system size is also not too small (a few thousand atoms at least, though depends what you want to extract).
NB: GULP is design to compute things without resorting to MD via lattice dynamics and so think carefully whether MD is even the best route to what you are looking for, especially since nothing much will happen in MD of magnesite until very high temperatures beyond vibration, which is well described by lattice dynamics in a more efficient way, especially below the Debye temperature.