The structure of liquid deuterium chloride by slow-neutron scattering

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Abstract
Measurements of the neutron scattering cross section for liquid deuterium chloride at 20°C are reported for incident neutron wavelengths of 0·7 Å and 0·5 Å. The diffraction pattern for momentum transfer/ħ, (Q), greater than about 6 Å-1 is due mainly to the molecular structure. The observed cross section has weaker oscillations than expected and, with the aid of a transform to real space, it is tentatively concluded that more than half of the molecules are in unusually strong interaction with their neighbours. This is further supported by the appearance in the pair correlation function of a broad peak in the region of 2·6 Å which it is suggested may be the liquified remnant of the ‘hydrogen bond’ observed in the solid phase. For longer distances the intermolecular, i.e. liquid, structure observed is weaker than predicted by recent simulation results and this may again be related to the unusually strong intermolecular interactions, or possibly to quantum mechanical effects. Our results are not dissimilar to other recent ones [16] but our measurement to much higher Q-values and the information it gives about the molecular structure leads to rather different conclusions.