Contributions from the atom less than M mass is considered as the faster time scaled motions than those from the atom more than M mass. See the more details about this in J. Phys. See the more details about these lengths in J. Phys. But in gener there will be coupling between those motions, so this leads the limitation of time scales. In Multiple time scale, I and J are the number of cycle that you want to calculate short time scaled and medium time scaled motions, respectively, before calculating long time scaled motion.
Delta t is the integration time step of long time scaled motions.
MTS-LN algorithm solves the simple Langevin equation and relies on position Verlet and on constant extrapolation. Followings are lists of possible selections. Scalar include fast and slow routine. This alleviates severe resonance problems and permits larger outer timesteps to be used for additional speedup. Any other combinations of options have not been tested.