[lammps-users] freezing molecules in a simulation

I am trying to run a MD simulation on the interface between bulk epoxy and graphite sheets. To do this, I am trying to freeze the graphite sheets in a planar conformation while still allowing them to contribute to the overall energy of the system. I was thinking that the fix freeze command would work for this, but I have no idea how to use it. Is it possible to freeze only a certain portion of a simulation? Can I declare the carbon atoms in the graphite sheet as their own atom type, and then freeze only this atom type? Any help would be greatly appreciated!!


Fix freeze (as well as other fixes) are applied to a group of
atoms. A "group" can be many different things - see the group command.
You can put just your graphite atoms into a group and then freeze them,
or use fix setforce to zero the force on them, or just don't time integrate
those atoms.