anchor.diff:    call bulk_change_el%create_time(hfile%observables, 'bulk_change', &
          bulk_change, ior(H5MD_LINEAR,H5MD_STORE_TIME), step=N_MD_steps, &
          time=N_MD_steps*dt)
  +  call omega_el%create_time(hfile%observables, 'omega', &
  +       omega(3), ior(H5MD_LINEAR,H5MD_STORE_TIME), step=1, &
  +       time=dt)
   
     if (dimer) then
        colloids% pos(3,:) = solvent_cells% edges(3)/2.d0
  
positive.code:   double precision :: kin_e, temperature
    integer, dimension(N_species) :: n_solvent, catalytic_change, bulk_change
    type(h5md_element_t) :: n_solvent_el, catalytic_change_el, bulk_change_el
  
    double precision :: colloid_pos(3,2)
    double precision :: com_pos(3)
  
negative.code:   call h5gcreate_f(correlator_group, 'mean_square_displacement', group, error)
    call h5md_write_dataset(group, 'value', msd%correlation)
    call h5md_write_dataset(group, 'count', msd%count)
    call h5md_write_dataset(group, 'step', colloid_sampling)
    call h5md_write_dataset(group, 'time', colloid_sampling*dt)
    call h5gclose_f(group, error)
  
    call h5gcreate_f(correlator_group, 'orientation_autocorrelation', group, error)
    call h5md_write_dataset(group, 'value', oacf%correlation)
    call h5md_write_dataset(group, 'count', oacf%count)
    call h5md_write_dataset(group, 'step', colloid_sampling)
    call h5md_write_dataset(group, 'time', colloid_sampling*dt)
    call h5gclose_f(group, error)
  
    call h5gcreate_f(correlator_group, 'planar_angular_velocity', group, error)
    call h5md_write_dataset(group, 'value', omega_acf%correlation)
    call h5md_write_dataset(group, 'count', omega_acf%count)
    call h5md_write_dataset(group, 'step', colloid_sampling)
    call h5md_write_dataset(group, 'time', colloid_sampling*dt)
    call h5gclose_f(group, error)
  
    call h5gclose_f(correlator_group, error)
  