T. YAMAGUCHI
Department of Chemistry, Faculty of Science, Fukuoka University, Japan
K. YAMANAKA
Central Research Laboratories, Organo Corporation, Japan
H. OHZONO
Department of Chemistry, Faculty of Science, Fukuoka University, Japan
M. YAMAGAMI
Department of Chemistry, Faculty of Science, Fukuoka University, Japan
H. WAKITA
Department of Chemistry, Faculty of Science, Fukuoka University, Japan
The structure of water in the sub- and super-critical state has been investigated with a newly developed rapid X-ray diffractometer using an imaging plate area detector. The temperature and pressure covered in the measurements were 300∼649 K and 0.1∼98.1 MPa, respectively, with nearly constant densities 0.7∼1.0 g cm-3 (Tc=647.3 K, Pc=22.12 MPa, ρc=0.322 g cm-3.) The chloride ion hydration in highly concentrated LiCl solutions in D2O has also been investigated in the temperature range 94∼648 K by pulsed neutron diffraction measurements with 35Cl/37Cl isotopic substitution. The X-ray radial distribution functions have revealed that the tetrahedral icelike structure has vanished in water above 416 K and 0.95 g cm-3 and that the short-range O-O interactions at ∼2.9 Å still exist at ∼40% for the coordination number of 3.9, though, with a large fluctuation and a distorted hydrogen bonding at 649 K and 0.7 g cm-3. The neutron data have revealed that the orientational correlation of water molecules around Cl- is greatly affected by temperature and almost lost above the critical point of water.