modify constraints
   method which     # 1
      constant const   # 2
      bonds bond       # 3
      iterations iter  # 4
      print pri        # 5
      tolerance tol    # 6
   end

This module has not be tested extensively and therefore should be treated as experimental. Modify contraint settings for molecular dynamics. which = none (preset) or shake or rattle. const = equilibrium (preset) or current. bond is the number of bonds to constrain, preset to 0. iter preset to 500. prin preset to 1000. tol preset to 10^-5.