anchor.diff:    call axial_cf%init(block_length, N_loop, N_loop*N_MD_steps)
   
     call colloids%init_from_file(data_filename, data_group, H5MD_FIXED)
  +
  +  ! center colloid in simulation box
  +  com_pos = sum(colloids%pos, dim=2) / size(colloids%pos, dim=2)
  +  do i = 1, size(colloids%pos, dim=2)
  +     colloids%pos(:,i) = colloids%pos(:,i) + (solvent_cells%edges/2 - com_pos)
  +  end do
   
     call input_data_file%open(data_filename, H5F_ACC_RDONLY_F)
   
  
positive.code:         v_com = v_com / tmp_mass
          kin_e = kin_e / 2
  
          call thermo_data%append(hfile, temperature, e1+e2+e3, kin_e, e1+e2+e3+kin_e, v_com)
          call axial_cf%add(i-equilibration_loops, com_pos, unit_r)
          call varia%tac()
       end if
  
negative.code:   integer(HID_T) :: polar_id
  
    logical :: do_rattle, do_read_links, do_lennard_jones, do_elastic, do_quaternion, do_solvent_io
    logical :: do_ywall
    integer, allocatable :: links(:,:)
    double precision, allocatable :: links_d(:)
    double precision :: link_treshold
  