Unknown Waters Separating from Water at Ice / Water Interfaces

<p>Interfacial phenomena in crystallization are crucial for understanding the process of phase transformation of materials. Ice crystallization is the most familiar crystallization phenomenon. Microscopic details of interfacial phenomena at ice-air interface have been extensively investigated with the help of abundant and sophisticated experimental techniques. However, interfacial phenomena at ice-water interfaces remain unclear because of the lack of experimental method. Amid this situation, the author has found, by classical in-situ optical microscopy, that unknown waters, which are separated from surrounding water by an interface, macroscopically appear at non-equilibrium interfaces between water and ice grown or melted by (de)pressurization in an anvil cell. The observations revealed varieties in morphology, dynamics and physical properties of the unknown waters. The unknown waters were suggested to have similar local structures with the structures of ices rather than bulk water, implying that the unknown waters can be pre-ordered state of water as mother melt before ice crystallization. Moreover, low-density unknown water and high-density unknown water were suggested to exist, providing implications on liquid polymorphism in a single-component system and the mystery of unique properties of water as liquid.</p>