modify dynamics
   criterion value        # 1
   #
      method meth            # 2
      step_size ps           # 3
   #
      update_list list       # 4
      archive arch           # 5
      print prin             # 6
   #
      scale_velocities vels  # 7
      scale_type which       # 8
      thermal therm          # 9
   #
      collision coll         # 10
   end

Modify the molecular dynamics methods. (1) The variable DYN_PASSED is set to true if the absolute difference between the ratio of the energy to the temperature at the start of the molecular dynamics and the same ratio at the end of the simulation is less than value times the average value of the ratio: |E_f/T_f-E_s/T_s| < value * <E/T>, the preset value is 0.1. The temperature targets are set in the modify environment block and can be met only if the velocities are reset periodically (see below).

(2) The equations of motion are integrated using one of three molecular dynamics method meth, the preset value is beeman, other legal values are verlet and calvosanzserna, the last being an experimental implementation which may not necessarily be a permanent feature. (3) A time step of ps picoseconds is used for the integration, the preset value is 0.001 ps or 1 fs.

During the simulation: (4) the non-bond lists are updated every list steps, preset value 25; (5) the coordinates and/or velocities are saved to the output archive file every arch steps, the preset value of 0 means that no archiving is done and (6) the energies are printed every prin steps, the preset value of 1 means that energies are printed every step which can lead to extremely large output files.

(7) Every vels steps, the velocities are adjusted (8) using one of four methods - scale (the preset value) or new as explained above (in modify environment) or andersen where the velocity of one atom, selected at random, is set at the target temperature ( vels should be set to 1 in the Andersen method); and berendsen which simulates the effect of a coupled heat bath; (9) the degree of coupling is expressed in the thermal collision time factor therm, the preset value is 0.1 ps.

Langevin dynamics can be calculated when a non-zero value is set for coll, the preset value of 0.0 ps^-1 sets the simulation for Newtonian dynamics.