Periodic boundary condition inside simulation box

Dear Lammps developers and users,
I have a system of a box of many particles interacting with each other. The boundary condition is set periodic. Also, there is one large particle located initially outside the box and moves toward the box.
Could you please guide me on how I can build this system? In other words, how can I build a smaller box with periodic boundary conditions inside the simulation box?


What you ask for makes no sense.

You cannot represent anything within a periodic system that is larger than the size of that system.
Thus you must make your system periodic at the scale of the large system, e.g. via replication.

Thanks for your explanation. Actually, the size of the periodic boundary box is not larger than the simulation box. please refer to the attached file for more representation.

It represents two snapshots of the system. As illustrated in the picture the blue and red particles are supposed to interact in a box region with periodic boundary conditions, and the purple particle enters the region. Could you please guide me on how I can define that box region with periodic boundary conditions?


You are still not making sense. You system either is periodic or not. And there is only one simulation box that contains all particles. So you cannot have a “periodic region” and you cannot have a “particle enter a periodic box”.

At any rate, this is a discussion about the science and not about LAMMPS and thus it is off-topic for this forum. Unless you have clarified the scientific reasoning for what you are trying to do - and that is a topic for a discussion with your adviser/supervisor/tutor/colleagues - and come up with a consistent and physically meaningful description, there is not much that I can do. Please understand that this is a technical forum and not a place to learn the science (even though it cannot be avoided to learn something when reading through some of the discussions).

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