Selecting PBC option for fracture toughness calculation

LAMMPS LAMMPS General Discussion
1

I am currently working on calculating the fracture toughness by drawing the strain-stress curve after introducing a crack into the sample. I plan to use the fix deform command as follows:
fix 2 all deform 1 z erate ${srate1} units box remap x.

Upon reviewing previous studies, I noticed that there are varying approaches regarding the application of periodic boundary conditions (PBC). Some papers apply PBC in all directions regardless of the strain direction, while others apply PBC only in the strain direction and use free surfaces in the other directions.

Could you kindly provide advice on which approach is more scientifically sound and reasonable for this type of simulation?

2

Those simulations simulate two different systems: without PBC you have a thin film, with PBC you have a bulk system. The choice of which is more suitable is a choice that you have to make yourself. You could also do both.

3

I see. Thank you very much for your kind advice!