Edge crack and problem with periodic direction

Hello to all lammps users
I ask this question few days ago, but now, I know what’s the problem and I really need your advice to solve it.
I want to create an edge crack in a periodic direction. I’m using neigh_modify command to turn of interaction between atoms between two regions. After few steps, because of periodic direction, one or two bonds come from the out of the box and then, the crack is no longer an edge crack. I can’t change the periodic direction. In the below link, you can see the problem

What’s your advice? I think this the best way to create a crack, should i use different method for crack or i can do something to solve in the current situation.

Thank you so much in advance and your help will be deeply appreciated.

Best regards,

Well there is no “edge” in a periodic system. it is

more like a slit crack in the middle of a bulk system.

There will be no interactions up to end points of

the slit, as defined by edges of the region. If atoms

move after that it just depends on whether they

are inside the region or not.