How to prevent box length change in non-periodic directions in LAMMPS?

[akohlmey]

@REHAD_SINDID_PATWARY

Could anyone suggest me is there any way to fixed this problem?

When posting in a public forum, you should make certain that you post to the correct category.
Questions about LAMMPS should go to one of the LAMMPS categories. Your post has nothing to do with the Materials Project. I have noticed your post by accident and will this time send it to the proper category, but don’t expect that to happen in the future.

For posting about LAMMPS you should first study Please Read This First: Guidelines and Suggestions for posting LAMMPS questions

@REHAD_SINDID_PATWARY

I am using non-periodic boundary conditions (s) along one axis (for example, the z-direction). However, during the relaxation simulation run, I observe that the box length in this non-periodic direction changes or expands with time, even though I want the dimension to remain fixed.

This is the documented behavior!
The “s” stands for “shrink-wrap” boundary conditions, i.e. the box dimensions follow the extent of the particles in that dimension.

@REHAD_SINDID_PATWARY

I understand that this behavior can occur due to thermal expansion, applied forces, or the use of certain fixes (e.g., fix nvt, pressure coupling, or atom loss at free surfaces).

Your understanding is not quite correct.

@REHAD_SINDID_PATWARY

I want to strictly keep the box dimension constant

So you should use “f” instead of “s”. Just check the documentation!