Neutron Scattering: Technique and Applications to Molten Salts

Abstract

Neutron scattering is a powerful, versatile and well-established technique capable of revealing the structural and dynamic properties of materials of ever increasing complexity at the atomic level. This article, resulting from a series of lectures given by the author at the NATO-ASI (advanced studies institute) on molten salts, consists of two parts. The first part gives an overview of the techniques of neutron scattering, its underlying theory, and methods of data collection and analyses. The major contribution of these techniques is the ability to determine, by using neutron diffraction isotopic substitution (NDIS) experiments, the individual partial structure factors (PSFs), S _αβ (Q), and pair distribution functions (PDFs), g _αβ (r), which is crucial in obtaining structural details of high spatial resolution. Since these distribution functions are the first in a hierarchy of inter-atomic correlations, they are the only ones directly accessible from experiments, computer simulations, and theory. The information obtained from such experiments can thus provide a critical test of the model potentials and liquid state theories. The NDIS methods can also assist in the analysis of spectroscopic (e. g., Raman) data, which are targeted at the identification of chemical species in a liquid. However, if these species are short-lived and not dominant, they will not be detected by the NDIS because the g _αβ (r) are average functions over all possible configurations and do not contain any information on individual species other than those that are long-lived and exhibit high degree of correlation.