I’m running simulations (both MD and CG/SD) on a system of atoms subdivided into to two groups. I want to impose the constraint that all of the atoms in any of these groups undergo identical displacements, such that the two groups can only undergo translations as separate units. Note that this is different from making the groups into rigid bodies, because i want to allow translation only, not rotation.
To achieve the above, I’ve used the commands
fix 1 bot aveforce 0.0 0.0 0.0
fix 2 top aveforce 0.0 0.0 0.0