Neutron diffraction experiments on liquid hydrogen halides HCI, HBr and HI are presented. For each sample the partial structure factors have been determined by isotopic substitution technique. Our data indicate that in each liquid the center-center structure factor is well reproduced by the structure factor of a monoatomic equivalent fluid and that the halide-hydrogen structure factor (which is sensitive to correlations between molecular and intermolecular axes) resembles the one derived by neglecting orientational correlations. This finding is in conflict with the presence of strong directional bonds as in the case of hydrogen bonded liquids. On the contrary orientational correlations between the molecular axes are clearly present in the hydrogen-hydrogen structure factors which markely differ from the uncorrelated model results.
