Size effect problem in periodic boundary

Dear LAMMPS Users,


I’m doing a fracture test with ( P P S ) boundary condition. The point is I’m observing different behavior with different size in xy plane, i.e. 10times lattice constant vs. 30times of it, which shouldn’t be seen to the best of my knowledge as it is bulk in x and y and also the critical distance between atoms near the boundary up to the simulation box in x and y is smaller that the 1/2 cut off distance of my potential. Any comment on how to fix it ?



What do you mean by “different behavior”? Ground state energy? Mechanical property? Thermal conductance?

Using Periodic Boundary conditions do not exactly reproduce a bulk. In many (most?), it mimic the bulk, as soon as you ensure that the length scale of the phenomena you simulate is “small” versus the periodic dimension.