Determining the Structure of Stable and Supercooled Liquids by High Energy X-Ray Diffraction

Abstract

The average structure of glass-forming liquids and glasses can be studied by high energy Xray diffraction (HEXRD) and can be directly compared to predictions by simulations. X-rays with high incident energy (>100 keV) are highly penetrating and provide scattering data to high values of scattering vector (up to 30Å-1). The beam spot sizes are small (typically 50-500 microns) and data acquisition time rapid (typically 0.1 to 0.5s), so relatively small samples can be studied and transient processes studied. By combining HEXRD with containerless techniques a series of refractory oxide liquid systems have been studied with the opportunity available to study deeply supercooled regions, the vitrification process and the influence of changing the partial pressure of oxygen. The scope of these studies has recently been extended to include molten salts and lower melting point liquids, these latter studies have been combined with state-of-the-art Molecular Dynamics simulations which allow full descriptions of the structure and dynamics of liquids to be developed.