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

In liquid phase, the H-bonded systems exhibit labile small clusters and the information about the average situation could be obtained through X-ray and neutron diffraction. In terms of scattering by groups X-ray scattering simplifies the intermolecular structural analysis considerably while the method of isotopic substitution with deuterated samples in neutron scatering yields informations about the intermolecular atom-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 atom-atom correlations are obtained in terms of model clusters. For typical H-bonded liquid e.g. water, the average intermolecular potential energy 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 computer simulation methods. These are also discussed in brief.