Synchrotron radiation studies on pressure-induced structural changes in liquids and glasses

Combination of synchrotron radiation sources and large-volume presses enables us to carry out in situ observations of structural change in liquids and glasses at high pressures up to several gigaPascals and high temperatures above 1200 o C. In this report, we present two examples: liquid Sn and SiO 2 glass. X-ray diffraction measurements were carried out on liquid Sn at 2.0 and 5.3 GPa. With increasing pressure, a shoulder of the first peak in the structure factor became less prominent and the ratio of the position of the second peak to that of the first peak decreased. These changes are attributed to a diminishing of the covalent structures remaining in the liquid state. Data on the temperature dependence of the x-ray diffraction by SiO 2 glass were measured up to 560 o C at 17 GPa. The sample crystallized to stishovite above 560 o C. While no drastic change was observed in the short-range order, a shift of the position of the first sharp diffraction peak to higher wavenumber and a sharpening of it were observed with increasing temperature. The shift and the sharpening suggest some relaxation in the intermediate-range order.