anchor.diff:          end do
           call varia%tac()
   
  -        call rattle_body_pos(colloids, links, links_d, dt, solvent_cells% edges, 1d-9)
  +        call rattle_body_pos(colloids, links, links_d, dt, solvent_cells% edges, rattle_pos_tolerance)
   
           so_max = solvent% maximum_displacement()
           co_max = colloids% maximum_displacement()
  
positive.code:         end do
          call varia%tac()
  
          call rattle_body_vel(colloids, links, links_d, dt, solvent_cells% edges, 1d-9)
  
          call time_flag%tic()
          call flag_particles
  
negative.code:   N_MD_steps = PTread_i(config, 'N_MD')
    dt = tau / N_MD_steps
    N_loop = PTread_i(config, 'N_loop')
  
    rattle_pos_tolerance = PTread_d(config, 'rattle_pos_tolerance')
    rattle_vel_tolerance = PTread_d(config, 'rattle_vel_tolerance')
  
    sigma = PTread_d(config, 'sigma_colloid')
    sigma_v = sigma
  