Structural studies of supercritical fluid metals using synchrotron radiation

Abstract X-ray diffraction (XD) and small angle X-ray scattering (SAXS) measurements for metallic fluids up to the supercritical region have been carried out using synchrotron radiation at SPring-8. We obtained the structure factor, S(k), and the pair distribution functions, g(r), for expanded fluid Se and Hg from the liquid to the dense vapour region by XD measurements. The spectra of dense Se vapour were observed for the first time. The structural change in the semiconductor–metal transition in fluid Se is discussed using the results of XD measurements. To obtain information on the density fluctuation in fluid Se near the critical point, SAXS measurements were carried out. Based on these structural data, together with previous results by X-ray absorption fine structure spectroscopy, we discuss how the density fluctuation affects the local structure and electronic properties of fluid Se near the critical point.