anchor.diff:    call elem% create_fixed(box_group, 'edges', L*1.d0)
     call h5gclose_f(box_group, error)
   
  -  call e_solvent% create_time(colloids_group, 'position', solvent% pos, ior(H5MD_TIME, H5MD_STORE_TIME))
  +  call elem% create_fixed(colloids_group, 'position', colloids% pos)
  +
  +  call h5gcreate_f(datafile% particles, 'solvent', solvent_group, error)
  +  call h5gcreate_f(solvent_group, 'box', box_group, error)
  +  call h5md_write_attribute(box_group, 'dimension', 3)
  +  call h5md_write_attribute(box_group, 'boundary', ['periodic', 'periodic', 'periodic'])
  +  call elem% create_fixed(box_group, 'edges', L*1.d0)
  +  call h5gclose_f(box_group, error)
  +
  +  call e_solvent% create_time(solvent_group, 'position', solvent% pos, ior(H5MD_TIME, H5MD_STORE_TIME))
   
     call solvent% sort(solvent_cells)
   
  
positive.code:   double precision :: epsilon, sigma, sigma_cut
  
    integer :: i, L(3), seed_size, clock, error
    integer, allocatable :: seed(:)
  
    call random_seed(size = seed_size)
  
negative.code:   type(h5md_file_t) :: datafile
    type(h5md_element_t) :: elem
    type(h5md_element_t) :: e_solvent
    integer(HID_T) :: colloids_group, box_group, solvent_group
  
    integer, parameter :: N = 1000
    integer, parameter :: N_colloids = 3
  