boundary plan

Please post to the list, not to me.

Again, “boundary plan” is not a LAMMPS
term. If you mean, how do I create this
boundary in LAMMPS, then you can look
at the lattice command and its orient options.
You can make, for example, a planar tilt GB,
by using lattice, create_atoms for atoms
on one side of the boundary, then lattice, create_atoms
again for the atoms on the other side.