In my simulation, everything was running smoothly with an aluminum plate. However, when I replaced the aluminum plate with an iron plate, the simulation stopped in between without any error messages. What could be the reason?
You have to provide a better description of your simulation set up as well as of the problem you are encountering. Have a careful read of this post Please Read This First: Guidelines and Suggestions for posting LAMMPS questions and reformulate your issue.
There may not be any error messages in the LAMMPS log file, but there can be multiple different indications that errors have happened or your job was terminated (inside of LAMMPS or outside). Essentially, no calculation is stopped without any indication.
How should anybody know without the opportunity to either observe what you are doing or being able to reproduce what you see independently. Please remember that in science, no observation has any value unless it can be independently reproduced. You just have to get into the habit to treat any unexpected behavior of LAMMPS like a science project and document it accordingly. Just posting something like “XXX doesn’t work, what is the reason?” without any context is the opposite of that.