anchor.diff:    type(h5md_element_t) :: elem_T
     type(h5md_element_t) :: elem_v_com
     integer(HID_T) :: box_group, solvent_group
  +  integer(HID_T) :: fields_group
     type(particle_system_io_t) :: solvent_io
   
     integer(c_int64_t) :: seed
  
positive.code:   use h5md_module
    use particle_system_io
    use mpcd
    use threefry_module
    use ParseText
    use iso_c_binding
  
negative.code:   call tz% init(0.d0, solvent_cells% edges(3), L(3))
    call rhoz% init(0.d0, solvent_cells% edges(3), L(3))
    call vx% init(0.d0, solvent_cells% edges(3), L(3))
  
    solvent_io%force_info%store = .false.
    solvent_io%species_info%store = .false.
  