Two liquid phases of water in the deeply supercooled region and their roles in crystallization and formation of LiCl solution

The properties of supercooled liquid water and the mechanism of crystallization in it were investigated using time-of-flight secondary ion mass spectrometry and reflection absorption infrared spectroscopy. The self-diffusion of the water molecules commences at 136 K, and then the liquid-liquid phase transition occurs at 160-165 K. The latter is evidenced not only by the occurrence of fluidity but also by the formation of a LiCl solution. The infrared absorption band also changes drastically above 160 K due to crystallization of water (on the Au film) and the formation of LiCl solution (on the LiCl film). The immediate crystallization and dissolution of LiCl are thought to be characteristic of normal water that is created in a deeply supercooled region, indicating that viscous liquid water (T > 136 K) is transformed into supercooled liquid water at around 160 K. The crystallization kinetics is different between these two phases because the former (latter) involves nuclear growth (spontaneous nucleation). Without nuclei, crystallization is quenched below 160 K in the present experiment. It is suggested that the viscous liquid phase coexists at the surface or grain boundaries of metastable ice Ic.