STRUCTURAL STUDIES ON EXPANDED FLUID MERCURY AND SELENIUM

Recent experimental results on the structural properties of expanded fluid mercury (Hg) and selenium (Se) obtained in our laboratory are reviewed. The energy-dispersive X-ray diffraction measurements for these fluids have been carried out for the first time up to the supercritical region including the metal-nonmetal transition region. From the measurements for fluid Hg in the density region from 13.55 to 6.8 gcm-3, it was found that the volume expansion of liquid Hg is not accompanied by a uniform increase of interatomic distance, r1, but mainly caused by a decrease of coordination number, N1 Our experiment for fluid Se also revealed that the twofold coordinated structure is largely preserved even in the metallic region near the critical point.