Intra- and inter-molecular terms in the structure factor of liquids

Abstract

A methodology for the analysis of the structure factor of molecular liquids obtained by neutron scattering at large momentum transfers in terms of molecular structure and intermolecular interactions is reported. First, an accurate adjustment of the intramolecular term at large angles is obtained; the stability of the fit, the analysis of the covariance matrix and of the quality factor when varying the investigated q range are severe tests of a correct evaluation of the short-range rigid interactions. Subtracting the intramolecular contribution, it is then possible to reach the intermolecular term, giving access to smoother interactions remaining in the low q-range. Applications to the characterisation of libration in C 2D 6, H-bonding in N-methylformamide and to the analysis of urea–urea interactions in water are given.