RELATIONSHIPS BETWEEN THE DIELECTRIC AND STRUCTURAL-PROPERTIES OF SUPERCOOLED LICLRH2O SOLUTIONS

The relation between the dynamics of dielectric relaxation, the glass- forming ability and properties in the supercooled state of LiCl : RH2O solutions are investigated, via measurements of the dielectric spectr a between 45 MHz and 20 GHz and temperatures between 210 K and 300 K a nd concentrations R less-than-or-equal-to 20. For high concentration g lass-forming solutions, a close correspondence between the temperature dependencies of the Cole-Cole relaxation time tau(C), the conductivit y, and the viscosity, is observed. Tau(C)(T) is well-described by a po wer law form (T-T(MC))gamma, with T(MC) approximately 205 K and gamma approximately 2, a form motivated by mode-coupling theory. The data su ggest that non-Debye response at room temperature is associated with t he ability to vitrify at low temperatures. A microscopic basis for the avoidance of crystallization is provided by obtaining from the dielec tric data the mean radius available to a water molecule, which is show n to approach 1.9 angstrom in the highly concentrated solutions. This suggests strong confinement of water molecules by the ions, which prev ents macroscopic crystallization from occurring when cooled.