Error: Lost atoms (box explosion)

LAMMPS LAMMPS General Discussion
1

Hello everyone,

I am working on simulation of a polymer system at high temperature using ReaxFF. When I subject my polymer (~9000 atoms confined in a box) to high temperature, it exploded near 935K. I am trying to figure out a reason for that.

While the other ReaxFF energies (bond energy, angle energy, lone pair energy etc.) did not change significantly during explosion, one parameter (charge equilibration energy, Eqeq) did change significantly. Here’s a graph of final 10 data points of Eqeq before explosion:

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I am thinking therefore, studying why charge equilibration energy showed a surge, might offer an explanation of why the box has exploded.

Do you know what changes to make in charge-related commands such as:
fix 1 all qeq/reaxff 1 0.0 10.0 1.0e-6 reaxff

SO that the box won’t explode?

2

Your are looking at this the wrong way. Rather than forcing the system to behave in a specific way, you should try to figure out why it doesn’t. That explanation will tell you whether the behavior is inconsistent and how to address it (if at all).

What do you know about the chemistry of your polymer? Is it stable at your chosen temperature?
What do your know about your ReaxFF parameter set? Is it supposed to be transferable to your compound and - more importantly - the temperature range that you are applying. ReaxFF parameterizations are typically very specific and not very transferable (unlike simpler, non-reactive models).

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