Structural characterization of an electrolytic aqueous solution, LiCl⋅6H2O, in the glass, supercooled liquid, and liquid states

Abstract

Using the technique of hydrogen and deuterium substitution, the structure of water in concentrated lithium chloride aqueous solutions (LiCl⋅6H2O) is explored for the liquid, supercooled liquid, and glass states. It is found that changes in structure between the glass and supercooled states are minor, but that a major change in water structure occurs as the supercooled liquid is heated above the temperature of peritexy of the penta-hydrate (Tp=207 K). In particular the 4.4 Å peak in the OO pair correlation function of pure water, which is normally viewed as indicating tetrahedral short range coordination in water, is absent in the LiCl solution at the same temperature, but reappears strongly in the glass and supercooled states. Corresponding changes occur in the HH and OH correlation functions. In addition, correlations appear to extend nearly twice as far in the glass and supercooled liquid, compared to the room temperature liquid.