Periodic boundary condiion

Dear LAMMPS experts,

When periodic boundaries are applied, how should the length in that dimension be interpreted? Is it considered infinite, or is there a specific way to calculate its effective length?

To provide context, I am working on calculating the moment of inertia for a 3D cantilever with dimensions L, h, and w along the x, y, and z axes, respectively. In this case, I have applied periodic boundary conditions along the z-axis.

Your insights would be greatly appreciated!

Best regards,
Bahman

You need to work out yourself how the PBC affects the physics of your cantilever. Think about applying forces in these two cases:


In case a) the cantilever will act as an infinite rod, assuming that the force applied is much smaller than the internal forces.
In case b) the cantilever will respond as a rigid object of length L=zhi-zlo.

In both cases, the forces are also applied to the periodic images. This should be clear if you know how PBCs work.