NEUTRON-DIFFRACTION PLUS MOLECULAR-DYNAMICS - A POWERFUL APPROACH FORUNDERSTANDING LIQUID STRUCTURE

The local order present in liquids gives rise to features in the pair distribution function (pdf) derived from neutron diffraction that cann ot be interpreted directly. One powerful approach to deriving structur al information from the intermolecular region of the pdf is to simulat e the liquid by means of molecular dynamics. The quality of such simul ations is normally tested by the extent of agreement with the experime ntal energy and pressure. However, the additional requirement of repro ducing the experimental pdf provides an exacting test of the quality o f the simulation, If the initial agreement is poor, the simulation may be improved by adjustment of the parameters describing the interatomi c potentials until satisfactory agreement is attained. It is then poss ible to interrogate the simulation in order to derive structural infor mation regarding local order in the liquid. The method will be describ ed in outline and exemplified by application to bromotrifluoromethane.