anchor.diff:    type(thermo_t) :: thermo_data
     double precision :: temperature, kin_e
     double precision :: v_com(3)
  +  double precision :: com_pos(3)
  +  double precision :: unit_r(3)
     type(particle_system_io_t) :: dimer_io
     type(particle_system_io_t) :: solvent_io
     double precision :: bulk_rate
  
positive.code:      call dimer_io%velocity%append(colloids%vel)
       call dimer_io%image%append(colloids%image)
  
       solvent_cells% origin(1) = threefry_double(state(1)) - 1
       solvent_cells% origin(2) = threefry_double(state(1)) - 1
       solvent_cells% origin(3) = threefry_double(state(1)) - 1
  
negative.code: 
    integer, dimension(N_species) :: n_solvent
    type(h5md_element_t) :: n_solvent_el
  
    integer, parameter :: block_length = 8
    integer :: n_blocks
    type(correlator_t) :: msd, oacf
    integer(HID_T) :: correlator_group, group
  
    type(histogram_t) :: z_hist
    type(h5md_element_t) :: z_hist_el
  