Calculate change in scalar variables between timesteps

LAMMPS LAMMPS General Discussion
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1

Hello!

I’m trying to simulate a packing in where a box filled with spherical particles with gran/hooke potential is isobarically compressed such that density is monotinically increasing, and average contact number/atom increases over time.

I can monitor the change in density and average number of contacts/atom through thermo_style, but I wish to implement an exit condition which monitors the change of these two variables between every N timesteps.

(To clarify: Exit condition should be that if the change of the two scalar values is smaller than a set tolerance, the script should exit.)

Is this possible?

2

It could probably be done using the fix vector command — LAMMPS documentation

That would allow you to store properties every N timesteps.
Then you just need an equal style variable that computes what index you have to use for a given timestep and then another that computes the difference between the fix vector item for that step and the previous item.

3

Thank you for the quick response. This worked great, had to add a variable handling a logical argument to ensure I didnt reach out of scope at first iteration. (1 and 1 instead of 0 and 1)