Neutron diffraction plus molecular dynamics: a powerful approach for understanding liquid structure

The local order present in liquids gives rise to features in the pair distribution function (pdf) derived from neutron diffraction that cannot be interpreted directly. One powerful approach to deriving structural information from the intermolecular region of the pdf is to simulate the liquid by means of molecular dynamics. ality of such simulations is normally tested by the extent of agreement with the experimental energy and pressure. However, the additional requirement of reproducing the experimental pdf provides an exacting test of the quality of the simulation. If the initial agreement is poor, the simulation may be improved by adjustment of the parameters describing the interatomic potentials until satisfactory agreement is attained. It is then possible to interrogate the simulation in order to derive structural information regarding local order in the liquid. thod will be described in outline and exemplified by application to bromotrifluoromethane.