This is the user who recently started LAMMPS.
I am interested in polymer reactions using LAMMPS and am calculating epoxy-amine reactions.
I am referring to the paper below.
One question is that we used Distance regimes and Restrain settings to shorten the calculation time of possible bonds in the paper, and I wonder if this can be implemented with LAMMPS.
What command should I use in LAMMPS if I can implement it?
Performing advanced ReaxFF based simulations is not something that you should be doing when you are a new LAMMPS user (and probably new to MD as well?).
Please also note that the paper you are referring to what published by the van Duin group, who have their own implementation of ReaxFF. The one in LAMMPS was originally a re-implementation called PuReMD, but has been refactored a few times, so it has some parts that are quite different now. Because of being an alternate implementation, the REAXFF package in LAMMPS may not contain all the features present in the van Duin group code.
So you need to study very carefully what features and what MD code they were using.
To know more details about how to realize what is described, you need to follow the information from the paper and failing that, you should contact its authors.