Structure of water under high pressure and temperature, 2

Katayama, Yoshinori; Hattori, Takanori   ; Saito, Hiroyuki; Aoki, Katsutoshi; Funakoshi, Kenichi*; Tange, Yoshinori*

Liquid water at ambient conditions shows unique properties because of hydrogen-bonded network structure. We conducted high-pressure high-temperature X-ray diffraction experiments up to 17 GPa at the SPring-8 synchrotron radiation facility and reported that the local structure changed towards a simple liquid-like structure through an increase of coordination number. We have extended the pressure range to 20 GPa and the results will be reported. However these data were measured just above the melting temperature at each pressure so that the effect of pressure (density) and that of temperature could not be separated. In this work, we have conducted X-ray diffraction measurement at various temperatures near 1 GPa. The shoulder of the first peak in S(Q) vanished at 200 C and the first peak became symmetric at 600 C. This result suggests a structural change from a low coordinated structure to a simple liquid-like structure.