MOLECULAR CLUSTERS AND CORRELATIONS IN H-BONDED LIQUIDS THROUGH X-RAYAND NEUTRON-DIFFRACTION

In liquid phase, the H-bonded systems exhibit labile small clusters an d the information about the average situation could be obtained throug h X-ray and neutron diffraction. In terms of scattering by groups X-ra y scattering simplifies the intermolecular structural analysis conside rably while the method of isotopic substitution with deuterated sample s in neutron scatering yields informations about the intermolecular at om-atom correlations. The two methods when combined together give very useful informations about the existence of distinct dusters in liquid state. A cluster structure function is defined and intermolecular ato m-atom correlations are obtained in terms of model clusters. For typic al H-bonded liquid e.g. water, the average intermolecular potential en ergy function shows peculiar features which die out gradually at high temperatures and H-bonded features could be represented very well by S .W. model potential. Information about the intermolecular correlations can be obtained through RISM integral equation and also through compu ter simulation methods. These are also discussed in brief.