STRUCTURE AND DYNAMICS OF SUPERCOOLED AND GLASSY AQUEOUS IONIC-SOLUTIONS

X-ray diffraction, neutron diffraction isotopic substitution(NDIS), an d quasi-elastic neutron scattering(QENS) measurements have been made o n concentrated aqueous solutions of lithium halides LiX (X=Cl, Br, and I) in a temperature range covering the room-temperature liquid, the s upercooled liquid, and the glassy state. X-ray radial distribution fun ctions have revealed that the hydration shell of the halide ions is gr adually structured with lowering temperature. Another interesting feat ure is the evolution of water-water interactions centered at 4.3 and 6 .9 Angstrom independent of the halide ions, due probably to reinforced hydrogen bonds at low temperatures. The NDIS radial distribution func tions related to Li+ and Cl- have demonstrated that the orientational correlation of bound water molecules for Cl- is more strongly temperat ure-dependent than that for Li+. At low temperature the formation of a second hydration shell of Li+ and Cl- has been established. The QENS data have shown that the translational motion of water molecules in th e LiCl solution is more hindered with lowering temperature. The struct ural and dynamic characteristics of the supercooled and glassy solutio ns are discussed in connection with nucleation of ice, isotropic reori entational motion of water, and the partial recovery of hydrogen bonds in these solutions.