Structural studies of a water/dioxane mixture by neutron diffraction with hydrogen/deuterium substitution

Neutron diffraction measurements have been made of a 0.167 mol fraction mix ture of deuterated 1,4 dioxane in water. Measurements were made for four di fferent isotopic compositions of the H2O/D2O water to separate the partial structure factors of the hydrogen atoms in the water molecule. A MCGR techn ique was used to analyse the data. The results show strong spatial correlat ions arising from the hydrogen bond network for the water which have simila r features to those observed in the pure aqueous phase. It appears that the dioxane molecule is incorporated into the water network with little distor tion of the local correlations. A large small-angle scattering signal was o bserved at low e-values which varied according to the H/D contrast. This fe ature can be fitted by the MCGR routine and may relate to some ordering on a mesoscopic scale. Further studies are in progress. (C) 1999 Elsevier Scie nce B.V. All rights reserved.