generating infinitely long chain in Lammps

Hello sir/madam,

Happy new year!
I have several questions when generating infinitely long chain based on periodic boundary conditions.
They are described in the file attached.
Thank you for your help.

Best regards,
Jiayuan Miao

Questions.pdf (180 KB)

LAMMPS doesn't know anything about your chain and how long
it is. It simply knows about each bond and the 2 atoms in it.
If the bond crosses a periodic boundary, LAMMPS knows that
the 2 atoms are actually close together (the image of one of the atoms).

If you have a line of atoms, each bonded, and add a bond across
the periodic boundary, that is a ring, not an infiniite chain. You also
cannot have 2 different atoms on top of each other as you ask in your doc.